"True film speed" vs just developing the film more?

[m00dawg]

Something has been bothering me a bit as of late - comments like "X film is a 400 ISO film but really it performs like a 200 ISO film". Example include Fomapan 400 (I've heard things like it is better at 200 or 320) or Pancro 400 (which to me in 4x5 tends to give me thinner negatives using stock times if I rate it at 400). I'm also confused at the notion of "full speed" developers - that feels like a function of development time to attain the rated speeds. It's a question irrespective of just erring on the side of over-exposing the film a bit or intentionally pushing and pulling film.

I guess stated another way I'm not sure the relationship in development times when developing at box speed. If I'm buying a 400 ISO film I kinda expect I should judge it, at least initially, by its box speed. So if my negatives are thin, I feel like I should add time until they are the density I'm looking for then then, if desired, I might push or pull?

Or stated a third way, what is the difference in shooting, say, Fomapan 400 at 200 over just developing it longer and expose it at the box speed? Why is one better than the other (if it is)?

Hopefully that makes sense. It's been bugging me a bit because while I like the look of Pancro 400 for instance, in the 400 range I tend to lean on speed a bit more, especially in 4x5. If I don't have to worry about speed, I tend to use TMX (which I know looks very different from Pancro). If I want to take photos of flowers and it is slightly windy for example, having to loose a stop of speed before dealing with filters and what not changes things. HP5 I feel like I know well enough to be comfortable with it at box speed and pushed (I've gone as far as 1600 in 4x5 but I suspect I could go to 3200 and get good results with my process).

This is a general question but for what it's worth I tend to use XTOL (1:1 though lately I'm experimenting with replenishment).

[mrred]

All developers will exhibit the same properties, but there is a standard developer they use to test for box speed. That said, the toe of a film curve (shadows) becomes non-linear at a certain point and will not develop more when development time is increased. That is effectively the box speed. You can develop more and the mid to higher part of the curve will increase, but the toe will always stay at that box speed.

Some developers have different levels for the toe, as such, they are called speed-increasing or speed-reduction developers.

Effective Index (or EI) is not the speed of the film, rather just what the user shot/developed the film at.

[Bruce Watson]

You seem to be confusing exposure and development. They control different things, but they do interact somewhat. Exposure controls shadow density on your negative film, while development controls highlight density.

A film's "box speed" is determined under laboratory conditions using a specific developer at specific times, temperatures, and agitation techniques. Since this is just about impossible to reproduce by any of us without the required laboratories, equipment, and controls, what it is, is a guide. A place to start.

What the Zone System (Adams and Archer) addresses is how to find your personal exposure index (PEI, or just EI), and your personal normal "N" development time for your preference of developer, time, temperature, and agitation style.

If you'll put in the work reading, understanding, and then testing, you'll end up with a system customized to your equipment and techniques that allows you to control both your shadow detail and highlight detail, accurately and (more importantly I think) repeatably.

If you don't like the Zone System, there are dozens of variants out there. There's likely a method that fits the way you want to work if you'll look for it.

BTW, there's really no such thing as "pushing" a film. Exposing the film less records less shadow detail which you can not recover in development. What you get from the increased development is mostly an increase in highlight density. This can make the film easier to print in the darkroom, and it's also responsible for the increase in "graininess" of the "pushed film". But if you look hard at the shadows in the print, you'll find them lacking shadow details. Because you underexposed the film. Pushing is more accurately described as "under exposure + over development".

[Jac@stafford.net]

Rule of thumb with B&W: over-exposing a stop is better than under-exposing. Due to variables in processing (and in my case inaccurate LF shutters), it's all revealed after processing. (My shutters are all a little slow. So am I. :) ) ... for processing I begin with the manufacturers' recommendation. I'm stuck in my ways and use only D-76 and Rodinal and leave exotic developers to my heroes on this forum.

[Leigh]

So if my negatives are thin, I feel like I should add time until they are the density I'm looking for...
Negatives being thin has nothing to do with EI. It's controlled entirely by development.

Shadow detail is a function of exposure and EI, and cannot be changed by development.
If information is not in the latent image, no amount of development can create it.

- Leigh

[Pere Casals]

rated speeds.

Read Beyond The Zone System book, ebay $4

Read this: https://en.wikipedia.org/wiki/Film_speed


Definition of speed:

Any film speed (with certain non ISO processing) tells you that film toe is at 3.3 stops underexposure from what an "standard" meter says, so with an spot meter you know what scene spots are in the linear part of the curve, or underexposed enough to be in the toe. It is important to understand this because this is absolutely basic.

This is becasue speed is useful: you know what scene spots will be in the toe and what spots will be "acceptably" captured because of being in the linear share.


Definition of ISO speed:

As always, if using D-76 (or equivalent in speed) and using recommended standard development time you have the toe at -3.3 from what meter recommends, but you also have the ISO standard contrast.


If a rated speed (with certain processing) don't places toe at -3.3 this is not a film speed, this is a way to say how you expose.


FOMA 400 is not a ISO 400 film, it is 400 (non ISO) speed if developed with an speed boosting developer, but it has lower ISO speed with D-76. Datasheet says that 400 speed can be reached, but they should mention with what developer.

If using a "speed" the toe is not at -3.3 then this is not a film speed, but a way to say how one exposes.

[Jac@stafford.net]

All these posts regarding nuances are largely distractions.

[Pere Casals]

All these posts regarding nuances are largely distractions.

Jac, no distraction, the speed term is used around very bad, IMHO.

In the massive development chart (with some errors) and in datasheets we have development of TMX to obtain 50, 100, 200 and 400. Only the 100 is a ISO speed. The 50, 200 and 400 are non ISO EI because contast is not standard, and film toe may not be at -3.3 stops, one thing is pushing and another one is modifying film speed.

When someone says "I rate TMX at xxx speed" he usually says nothing about film speed, if he has calibrated his process then may be he is talking about film speeds, if not he speaks about his film usage.

[m00dawg]

WOW this was a ton of good info in a really short time. Thank you thank you thank you everyone! Great things to think about. I've working my way through The Negative right now but it's a dense book and I may need to re-read it hehe. It sounds like the specific piece of the puzzle I was missing was the relationship between the toe and the box speed. That didn't click until now.

[Pere Casals]

WOW this was a ton of good info in a really short time. Thank you thank you thank you everyone! Great things to think about. I've working my way through The Negative right now but it's a dense book and I may need to re-read it hehe. It sounds like the specific piece of the puzzle I was missing was the relationship between the toe and the box speed. That didn't click until now.

Let me insist, read Beyond The Zone System, a flawless explanation about how the thing works.

[Jac@stafford.net]

In the massive development chart (with some errors) .

With very many errors. The Massive Development data is deficient in two regards: first it accepts user experiences which, in my opinion are ill founded, full of poor practices and second: many charts are simple numeric extrapolations, and we should know that is a wrong way.

[m00dawg]

Let me insist, read Beyond The Zone System, a flawless explanation about how the thing works.

Ooops I thought you meant the Zone System as covered in The Negative. Noted! Took a peak at the preview and TOC on Amazon and yes this looks quite fantastic for the subject at hand (latest revision was updated in 2013 as well!?). Added to my list of must-have books, thanks!

[Pere Casals]

With very many errors. The Massive Development data is deficient in two regards: first it accepts user experiences which, in my opinion are ill founded, full of poor practices and second: many charts are simple numeric extrapolations, and we should know that is a wrong way.

Ok... don't consider the Development Chart, let me correct my statement: just see recommended developments in the TMX datasheet for diverse speeds:

> 100 speed is ISO, it is for sure that the toe is at -3.3 stops with recommended standard processing, and it delivers standard contrast.

> 200, 400, 800 EI are film Exposure Index, non ISO, and not speeds. With the recommended development by kodak the toe may not be at -3.3 so it isn't with a new speed, but a way to make a printable negative. For this reason the say EI and not Speed:

186477



> Somebody saying he rates TMX ISO 80, this is not a film speed if he made no calibration, this is how he shots... , this is also for sure.

> Using a high speed developer would modify the film speed, this is: it modifies the required exposure for a spot to be in the linear region and outside the toe.

[Neal Chaves]

Let me insist, read Beyond The Zone System, a flawless explanation about how the thing works.

If you follow Adams' recommendations in his book The Negative, and don't take all his disclaimers into consideration, you will make nothing worth printing. Ever see that photo of him dressed as Moses with the Ten Commandments done by his followers? The highlights are all blown out and the shadows are opaque because the negative was so thin they had to print on #4. At least Davis reveals in his complicated system that the effective speed of TRI-X developed in HC110 B for 5:00 at 68* is 64. Picker claimed some complete understanding of Adams' system and offered to give you your personal EI for $5 if you send him your test negative to measure. Adams hated Mortensen , probably because of all the beautiful women that posed for Mortensen, but his book "Mortensen on the Negative" shows you how to read a negative without a densitometer and make the appropriate adjustments.

[Pere Casals]

Davis

Yes... one thing is a recipe to get a working method and another one is BTZS. There are many good recipes out there, everyone is good if we make some personal adjusments for it.

But basicly BTZS is not a recipe, it's a compendium about technical sensitometry. It (primarily) not tells you how to expose/process, it tells what we'll obtain depending on how we expose, process and print.

With a calibration and a spot meter we can predict what particular density we'll obtain in the negative for an scene spot, and the same for the printing process. So it opens the scope of photographer's mentality.

BTZS is advanced knowledge that may not be necessary most of the times, but if we want to adjust (for example) a reversal processing it will save a lot of repetitive testing.

[Doremus Scudder]

You know, all the information above is correct. It just seems to me that we often dump more information and techno-babble on to someone looking for a basic, halfway-easy-to-comprehend answer that we risk overwhelming them with detail.

Let me attempt a simpler, albeit less-detailed, reply directed at the OP's questions:

First, as mentioned above, standard ISA film speed is determined by lab testing with specific parameters for exposure, developer and amount of development.

In practice, any of these parameters can be different for us.
1. If we use a different developer, it might not give the same film speed as the lab standard. This happens all the time. Differences are in the range of one-stop slower to a bit faster (the extremes being attainable only with more specialized developers). For example, HC-110, according to Kodak, will give an E.I. about a third of a stop slower than ISO standard.
2. We more than likely all meter differently than the lab standard, whatever type of metering we use. This affects where the low values get placed on the film. We may have to add more exposure for our way of metering to get the shadow detail we like.
3. We often don't like to develop as much as the ISO standard, usually to keep highlights from becoming difficult to print, etc. Changing development time has a small effect on film speed; less development = slower E.I. and vice-versa. We may need to adjust our E.I. to match our desired development time.
4. Finally, some smaller manufacturers don't rate their films so precisely to ISO standards, so they may be overstating their film speeds a bit. We need to test and adjust for that.

Yes, you should judge your film initially at published box speed and using the developer and developing time recommended by the manufacturer. But then, be aware that some of the above discrepancies will likely come into play and you'll have to make adjustments. If you don't feel like learning the Zone System or whatever right away, just follow Kodak's age-old advice: "If your negatives consistently have too little shadow detail, increase your exposure (i.e., slower E.I.). If your negatives are consistently too thin (i.e., underdeveloped so you don't get light enough highlights), then increase development time (and vice-versa)."

Keep in mind that exposure determines how much shadow detail is recorded on the film. This is a function of the built-in speed of the film and can't be changed very much by development; just by a little as mentioned above, and that usually on the slow side.

Development controls the contrast spread from the more-or-less fixed shadow details to the highlights. We can increase the contrast (difference in density on the negative) between low and high by increasing development and vice-versa. We fine tune our development time to find the best compromise for us. Zone System users have different development times for scenes with different contrasts, but many just find a good middle time and use the contrast controls available when printing to make up the difference (especially roll-film users who can't easily switch development times for different frames). The idea is to be in the middle of your adjustments for a "normal" situation so you have room on either side to deal with more or less contrasty scenes.

One comment about "pushing": As mentioned above, this is basically intentionally underexposing the film (i.e., losing shadow detail and placing the highlights somewhere on the usual mid-range of the negative) and over-developing (to get those muddy highlights up to where they should be!). This results in a printable negative with a lot of separation between tones and no detail in the darkest shadows. This is fine for many low-light situations where making the shot would have otherwise been impossible; it is even a "look" that people have learned to like and so gets used for "normal" situations as well. If you want full shadow detail, however, you need to make sure you have enough exposure. How much shadow detail is enough for you determines your E.I. for any particular situation.

Hope this helps,

Doremus

[Luis-F-S]

Keep in mind that exposure determines how much shadow detail is recorded on the film. This is a function of the built-in speed of the film and can't be changed very much by development; just by a little as mentioned above, and that usually on the slow side.

Development controls the contrast spread from the more-or-less fixed shadow details to the highlights. We can increase the contrast (difference in density on the negative) between low and high by increasing development and vice-versa. We fine tune our development time to find the best compromise for us. Zone System users have different development times for scenes with different contrasts, but many just find a good middle time and use the contrast controls available when printing to make up the difference (especially roll-film users who can't easily switch development times for different frames). The idea is to be in the middle of your adjustments for a "normal" situation so you have room on either side to deal with more or less contrasty scenes.

Doremus

Required shadow detail also determines the effective film speed because the low value densities (Zone I-III) are set largely by exposure with development having very little effect on them. As noted, if you don't get the information on the film, no amount of development is going to bring it out. Use the film speed that will give a Zone I density approximately 0.1 density unit over the film base plus fog (fb+f). Develop the film to give a Zone VII exposure a density reading of approximately 1.15 over the fb+f. This requires a densitometer, however and I think I've offered to ready anyone's negatives who sends them to me for the cost of a SASE (as long as it doesn't get out of hand which I doubt it will). Cheaper than Fred's $5 cost as Neal noted. For the same $5 you can buy a used copy of Picker's the Zone VI workshop, which is more readable and easier to understand than Adams' the Negative. Just PM me for the address if you want me to read your negatives.

[Drew Wiley]

I'll stay on the sidelines chuckling this time.

[m00dawg]

Thanks for the discussion folks! I ordered Beyond the Zone System as it seems like a great read but also learned quite a bit just right here. In regards to the offers to do density testing of films, it sounds like to do that I would need to shoot a gray card or a test card in expected lighting setups to get good data from that? I'm not sure I'm quite ready for that but I do think it's a worthy exercise.

For now I am still seeing that Pancro 400 seems to work better more at 200 given my meter, lens, and subject combinations so far. I get better shadow detail. Admittedly I'm not properly using the zone system in these cases and it's been in shade or artificial lighting. I suspect a bright sunny day with a very wide dynamic range will be different (from what I've read, Pancro 400 provides a bit more shadow detail than HP5 in this regard). I definitely like it, not sure if I like it more than HP5 yet though. I still need to do some portraits with it and more shooting in general, but will probably shoot it closer to 200 until I work my way through BTZS, The Negative, and am able to consider doing some testing.

I do agree with some of the sentiments that one can over-complicate this to the point all I'm doing is taking lab shots. I don't want to go that far, and I do have a tendency towards over complication :) But I think getting a better handle on negative exposure and evaluating things would be helpful. I'm not applying it particularly well but I do think I favor the zone system, at least when doing serious shooting in 4x5. For 35mm, I think just adopting a pull/push mentality tends to work better for me since the photos are more snapshots and tend to be taken with haste. HP5 at 800 tends to work well for me - I like the look and I get good negatives so I'm not too bothered by it. 4x5 is certainly another story - part of the reason I shoot it is because it's methodical and it stands to reason being more calculating about exposure makes a ton of sense to me.

[Drew Wiley]

You don't shoot a gray card, but work with either a transmission step tablet or reflection gray scale, containing a full range of gray values from black to white. This is then measured with a densitometer and plotted. All a gray card does is indicate "middle gray" (Zone V), which might or might not indicate the middle of the true film scale. Simple gray card readings work better in color photography.

[m00dawg]

Aha ok good to know. Do you still need to meter for that (since how you meter would be part of this equation?). Could be quite the combination if testing the meter, the lens, the film, and the lighting.

[Pere Casals]

You are on track. With BTZS, I'd recommend you make the necessary effort understand every bit of knowledge in the first half. The logarithmic math is essential because it's all based on that. Don't think you will have to use all that theory in practice, but by understanding well sensitometry you will be aware of what you are doing in any situation.
____


Pancro 400 seems to work better more at 200

Just acquire that knowledge, then you will know why 200 works better with the way you meter. With an spot metering you will know what density will have any that spot of the scene in the negative, if tonality is compressed there or not in that spot, and you will know what development require that sheet to craft the visualization you want, and if the negative will be easy to print. I encourage you to get that knowledge. Next step is to use that tool for aesthetics, this is the difficult part to me.

That level of control is not always necessary, but exposing a LF sheet may require a remarkable effort, so nailing things is essential. With rolls we bracket on a doubt, this may be cheaper than thinking, but a photographer like John Sexton does not bracket, he rather makes two shots with same settings to have a backup, and he does it because he has all under control.

[Doremus Scudder]

I'll stay on the sidelines chuckling this time.

A wise decision! :)

[Doremus Scudder]

I'll chime in again, on the side of simplicity, and offer another approach.

I've managed to arrive at a high level of technical excellence when it comes to exposure and development without a densitometer or using higher math. Not that I can't do math or understand logarithms; I just don't need it to calibrate my film exposure and development.

My approach is strictly visual and based on making a "proper proof" on the printing paper I use most (which, unfortunately changes every year now, but I digress...).
Making a print with the minimum exposure to render the clear area (rebate) of the negative close to maximum black on the paper is the key. Make a print leaving a strip of the paper uncovered by the negative (contact print) or by leaving a bit of space beside the negative in the carrier (enlargement) that will receive more exposure than the area covered by the negative. Make a test strip, dry it down and inspect it in light that you consider optimum for displaying prints (this is critical; too bright and you'll end up underexposing and vice-versa). Find the minimum exposure that renders the black of the rebate almost indistinguishable from the black of the uncovered stripe. Note all your parameters (exposure time, f-stop, enlarger head height, etc., etc.). That's your "proper proofing time."

Now, simply make a proper proof of a typical negative on your favorite paper, choosing a medium grade (2-3, or whatever gets you in the middle of your contrast adjusting possibilities) and evaluate. If shadow detail is lacking, you need to expose more (change your E.I.). If it is way up on the scale, you're exposing more than you need to. If the highlights are dull and gray, you need to develop more; if they're blown out blank white, you're overdeveloping. Make adjustments, make some more negatives and proper proof them till you get the results you want. That's it.

You can refine the above for contractions and expansions, all the different films you use and all developers you use. Quick, easy, no investment in precision equipment (i.e., no densitometer), etc.

I'm now to the point that when in the field I indicate which paper grade I wish to print on along with my development scheme (N, N+ etc.). I'm right on 75% of the time and only off by a grade the rest of the time.

There are a lot more refinements you can make after this, but getting these basic things right right away makes your life a whole lot easier.

I love reading about sensitometry and tone reproduction and I think it helps me with the nuances and details of the whole process; I just don't need it to find the right exposure and development for my films...

Best,

Doremus

[Pere Casals]

I've managed to arrive at a high level of technical excellence when it comes to exposure and development without a densitometer or using higher math.


The recipe you explain is really very good advice, and it's completely worth to follow, there is a lot of wisdom in it.

Using a recipe is perfectly fine, but if one knows well the theory then he also knows what the recipe is to work, when is to fail, and what to do insted.

Making a film calibration was a basic exercise in photography schools for very good resons.

About investment, my high precission Nuclear Associates (ex RX gear) was $20, or one can simply scan the Stouffer alongside the calibrations to compare with no additional cost. A lux meter is $15.

It's a personal choice, one may want to learn the theory or not, but by spending a weekend one may experiment a boost in his mentality. At leat one knows why is he doing what he is doing.

[Drew Wiley]

One can also buy a Calibrated Step Tablet, with each of the 21 steps already read on a densitometer and written down on the package. Then, for beginner purposes, one can do crude "visual densitometry". You take a sheet of opaque black cardboard and punch two small holes about 1/4" or less in diameter, several inches apart, using a paper punch or leather punch. The step tablet is ordinarily on a sheet of 4x5 film. You place the area you want to read in your own test negative under one hole, over a light box, then using the other hole, see which step on the official tablet most closely resembles the particular density on your own shot. I won't go into the whole procedure here, and only mention how you don't necessarily need to purchase an expensive densitometer just to get started.

[m00dawg]

Ah that's a good idea! I have a feeling in practice I'll be doing an amalgamation of all these, especially while I read the book - I don't plan on suspending all my photography until I figure all this out hehe.

On the tablets, something like this (https://ndtsupply.com/ndt-density-step-tablets.html#pricing)? They are more expensive than I thought so was curious if I'm looking in the wrong place (prices are similar on the usual sites).

[Pere Casals]

On the tablets, something like this (https://ndtsupply.com/ndt-density-step-tablets.html#pricing)?

No!!!!

http://www.stouffer.net/T2115spec.htm T2115, $7

Or the calibrated one $17, T2115C http://www.stouffer.net/Productlist.htm


You scan your negative alongside with the Stouffer and by comparing you have a densitometer !!! :)

Also soon I'll release this freeware: https://www.largeformatphotography.info/forum/showthread.php?150045-New-darkroom-calibration-software to make it easier.

You make the contact copies of the stouffer, you scan the stouffer and the copies, et voilà... you have the curves with a click. Just buy a $15 densitometer if you want absolute units for light, like in the kodak datasheets.

[m00dawg]

Oh haha that's MUCH BETTER!

[Drew Wiley]

Yes, thank you. There are indeed very expensive step tablets on glass used to calibrate densitometers etc themselves. But a basic Stouffer 21-step tablet on film should be around $40 or less. I suggest buying a new one. Old ones might turn up a lot cheaper, but also might have significantly yellowed over time, making them hard to use.

[m00dawg]

Agreed! Up to $40 seems worth it. Thanks so much Drew, and everyone! Learned a heckofalot and now have some homework to do :)

[m00dawg]

So I've been watching Ben Horne and Alan Brock's videos this morning while sipping my coffee. A thought occurred to me. Maybe I AM metering wrong. I recall reading in The Negative that lightmeters are calibrated to middle gray so that tends to be what I meter on. Sometimes I'll take the dark and light points, look at the range but also do an average and I'll usually set the shutter speed to that average.

That works - I get negatives, but I wonder if that's one reason why Pancro 400 seems slower. When I've shot it in 35mm I used on-camera metering for instance (though I recall those lightmeters, really any lightmeter, is tuned for middle-gray?).

Seems like I need to re-read that chapter. I'm having less issues with negative film but I've probably had more sheets of Velvia 50 exposed poorly than those exposed well (a few I felt I nailed though and I can understand why folks like Ben Horne pay so much money for 8x10 slide). I was conscious of the dynamic range but also still setting the shutter speed typically to the middle of the range, and I'm wondering if that's wrong (if I should be leaning on the highlights instead for slide and on the shadows for color negative).

That said, middle gray is meant to be Zone V? So as long as I'm within the dynamic range of the film I should, artistic license aside and expansion/contraction aside, have a well developed negative?

Sorry I know I'm kinda making things fly off the rails a bit with regards to the original question. And likewise it sounds like I need to do some (re)-reading as well :) But it was a thought I had this morning while checking out Ben's film reveal - absolutely stunning colors. He really knows how to use Velvia 50.

[Pere Casals]

That said, middle gray is meant to be Zone V?

First, what is middle gray ? Middle gray can be different things, see here the "Table of middle grays":

https://en.wikipedia.org/wiki/Middle_gray

But, yes... you identify in the scene what you want it to be the middle gray in the print and this is Z-V, so what the meter says +/-0. You may want to modify that, but this is the "Standard" way.

If using the "true speed" of the film to meter, those areas that are not underdeexposed beyond 3.3 stops will be in the linear zone, so with no compression in the tonality but, depending on the film, as you underexpose you may be having a quality loss, so you need to know how (with your film/process) areas at -1, -2, -3 and -4 will be. You may place what you want in Z-V instead in Z-VII, to record the shadows that would be lost, in that case you may develop a shorter time to not have too high densities from overexposed areas, this underdevelopment won't mess much in the shadows. Basicly this is the N+/- development: expose for the shadows but develop for the highlights.

You may also want a safety factor, a modern LF shutter when was sold new it had a +/-30% specs accuracy, so a 1/30 can be 1/20 or 1/40, so it can vary a full stop and still being in specs. With negatives better to have a little overexposure than having a loss in the shadows, with slides (velvia) you have to ensure that you don't overexpose, because in that case highlights are easily damaged.

The method explained by Doremus is perfectly good, my recommendation is that first study well the BTZS book and later follow what Doremus explained, then you will be ready to nail what you want. There is a point since you don't see the meter reading, but you are visualizing the densities in the negative without thinking much, and the way the print will look straight, and what you'll have to do to print your visualization from your negative.

After you reach that mental point you will be in control with little effort and you will be able to focus on what light does with subject. Something like riding a bicycle, when one has practice he is not thinking in how he has to move le legs to pedal, and he may look forward and travel. And of course you'll also know when you should make accurate meterings for a complex scene.

The important thing is that when you have a pitfall you understand what happened, and what you would do instead next time.

[m00dawg]

There Pere! That does indeed help clear things up (and give me for to think about and do as I should probably get around to timing my shutters...).

[Drew Wiley]

Well, no...just because you know what Zone 5 is, doesn't mean the specific film involved will span the actual scene contrast, because neither is a fixed number. It all depends. And there is simply no substitute for accurately measuring your shadow versus highlight endpoints when significant contrast is involved. There are all kinds of potential exposure models you can choose from, including those already mentioned. But any of these have to be implemented hand in hand with a lot of actual shooting, developing, and printing before it really becomes easy. But don't worry. The learning process is fun and rewarding too.

[Bill Burk]

On another site, another discussion, a fellow we call Photo Engineer said a film’s true speed is the point of inflection, the point at which instruments are capable of detecting the departure of the characteristic curve from base plus fog.

[Pere Casals]

the point at which instruments are capable of detecting the departure of the characteristic curve from base plus fog.

Bill, in fact this is the speed point, I guess, not the film speed.

But it's true that the film speed is calculated directly from the exposure in the speed point. (development also has to deliver the standard contrast to be the ISO speed.)

ISO standarizes the position of the speed point "m" as having 0.1D more density than unexposed areas (fog+base). The film speed instead is calculated from the exposure in the speed point to make an standard meter to aim x10 the exposure in the speed point, this is 3.3 stops.

[esearing]

Not sure that -3.3 stops works for reality. If I meter/place textured shadows (dark moss on underside of wet rock, shadowed underside of fallen tree) on zone 2-ish I get no texture. Zones 3-4 give better texture and shadow separation. I set the f-stop and shutter accordingly and keep my EI of 100 constant for FP4+. So in theory I should have a film speed closer to 50 for my processing style if I read all this stuff correctly. I guess I don't care what each zone's density is supposed to be, since i used multigrade paper which allows altering those relationships (somewhat). I focus on the high to low range and trying to fit it on the negative, and my final print may not represent the original scene's tonality.

[Bill Burk]

Bill, in fact this is the speed point, I guess, not the film speed.

But it's true that the film speed is calculated directly from the exposure in the speed point. (development also has to deliver the standard contrast to be the ISO speed.)

ISO standarizes the position of the speed point "m" as having 0.1D more density than unexposed areas (fog+base). The film speed instead is calculated from the exposure in the speed point to make an standard meter to aim x10 the exposure in the speed point, this is 3.3 stops.
By the way where you quote 3.3 you are rounding. It’s 3 and a third.

The 0.1 speed point also needs to meet the contrast parameters. My friend who sold me his sensitometer likes to point out why.

It’s because at the contrast parameters, the speed determined by Delta-X agrees with the speed at the 0.1 point
The speed in both cases now coincides with the outcome of Kodak’s first excellent print studies. That point is the 0.3 average gradient.

I like to point out that 0.1 is certainly easy to find and check. Even though the right place is 0.3 average gradient, it’s harder to mark that on a graph and two people might mark the same curves slightly differently leading to different readings.

So we get a quick reading of the speed by using the 0.1 speed point, and we stay connected with Kodak’s first excellent print studies at the same time.

It was a really good compromise when the 0.1 speed point was chosen... with the contrast parameters.

[Pere Casals]

Not sure that -3.3 stops works for reality.

From "true speed" definition, a spot at -3.3 will have 0.1D over base + fog, so it will be in the "m" speed point. Pre 1960 ASA change it was -4.3

If that spot has not 0.1D (over base+fog) then it wasn't a "true speed" but an EI (Exposure Index).

...or we had a flawed metering/exposure/processing



If I meter/place textured shadows (dark moss on underside of wet rock, shadowed underside of fallen tree) on zone 2-ish I get no texture. Zones 3-4 give better texture and shadow separation.


The "Image Quality" we have in the "m" speed point is in the limit yet, grain may be different, etc... one has to know how -4,-3, and -2 looks with his film/process, of course.

But we also have sound inaccuracies in the process:

> A new Shutter had +/-30% specs !

> Is aperture scale exact ?

> Accurate bellows compensation ?

> Did we meter with a probe on the GG ? Have we flare from lens and a from a large circle illuminating compressed bellows ?

> Is film aged ? Is developer aged ? temp/time/agitation control ?

> Are shadows in LIRF because a moderately long exposure ?


If we are very accurate and using a true speed we have -3.3 in the "m". If we are not very accurate then we overexpose (negs) 1 or 1.5 stops and then we are in the safe side. We say "we rate" TMX at 50, but what we do is resurrecting the pre 1960 safety factor !!!! :)

[Drew Wiley]

Ho hum... Just more rote stereotypes about films which in fact differ with respect to how deeply down you can dig into the shadows. It can be more than -3.3, and it can certainly be less. And all of this is relative to development protocol. Stronger development (higher overall gamma) typically raises and steepens the toe.

[Pere Casals]

Ho hum... Just more rote stereotypes about films which in fact differ with respect to how deeply down you can dig into the shadows. It can be more than -3.3, and it can certainly
be less. And all of this is relative to development protocol. Stronger development (higher overall gamma) typically raises and steepens the toe.

(This is for BW negative film. Slides have a remarkably different norm)


Yes Drew, it can be more or less than 3.3, but if it isn't 3.3 then you are not metering with the true speed of the film/processing.

The calculation of the true speed always uses 10x the exposure in the "m" (B+F+0.1D) speed point to set the meter point. So it's 3.3 or your speed is not the true one.

Another thing is the pool of inaccuracies we have in the metering/processing...

There is sensitometry and there are recipes, both work.

In other words, if you develop exactly normal and meter with true speed then areas at -3.3 will have 0.1D over fog+base. Why? Because ISO norm says it. And a ISO norm is an ISO norm, not tales.

Beware, the BOX speed may be rounded to a standard speed, normative allows it, but then the BOX speed has a little discrepance to the true speed we are speaking, this has also to be said.

[Drew Wiley]

I don't give a hoot about "true film speed", as if there is only one valid way to calculate that to begin with. I do care about specific shadow distribution on the toe of the film, which is affected by several variables. And in that respect, I see no substitute to assessing one's own "personal film speed" relative to specific film, developer, and Zone placement (if Zone theory is even used). I've retained four Pentax digital Spotmeters. They all precisely match over their entire range; and if any one of them deviates, I have it serviced. My oldest one is now too beat up to bother keeping alive on life support. But one is kept virtually brand new as a reference. I'm quite confident my meter readings are accurate. My development too. For nitpicky purposes, I'm able to keep dev temp within 1/10th deg F is necessary, which is complete overkill for ordinary work, for which I have a temp compensating timer anyway. Film designers can worry about the rest. And if a batch is off, when I happen to need complete predictability, I'll spot it. But for that kind of usage, best to stick with the majors in terms of quality control - Kodak, Ilford, and Fuji. Then I have lots of densitometer plots confirming the consistency of my own protocols.

[Pere Casals]

I don't give a hoot about "true film speed", as if there is only one valid way to calculate that to begin with.

It depends... if you develop like kodak TMX dataheet says you nail the H-D curve they show with real units. I checked it and I found it exact. But if you make a creative development then your true speed can be any.

Also you may want to calibrate what true speed you have with your pocessing... in that case you'll be calculating the true speed to place the "m" at -3.3 again.

If you have an inaccuracy of a full 1 deg F you'll change the contrast, but not much the true speed.

[Drew Wiley]

From the analytical standpoint what makes me suspicious of any alleged industry-wide standard is just how different certain companies tend to interpret their "box speed". As much as I like Ilford products, I've found every single one of their films to be rather over-optimistic in terms of rated film speed. They seem to interpolate it too far down onto the toe, perhaps for wish-it-were-so marketing reasons? I dunno. And this seems to be the case in most developers. Then there are those cheaper EU films that are unquestionably marketed using too-good-to-be-true speed ratings. But the kind of technical lab applications I have in mind, Pere, have to be a lot more accurate than anything you're describing. General photography, no.

[Pere Casals]

certain companies tend to interpret their "box speed".

Yes of course... Kodak TMax P3200 is 800 true speed, and Ilford Delta 3200 is 1000... to say remarkable examples.

Foma 400 is another example of fake 400 IIRC, and CMS 20 with Adotech II... better at ISO 6.

For this reason it makes sense knowing very clear what's a true speed, because if using it you know where is the "m", and how far an spot in the scene is from m.

Many other films are well rated by the box lettering. We all know what films are...

[Drew Wiley]

I call it the BS coefficient. The faster that can be quantified, the better off we all are.

[Pere Casals]

Yes... :)

[Bill Burk]

I could see being suspicious of the speeds in the day of H&D but with ISO speeds I am confident that we can check them.

[Neil Purling]

Negatives being thin has nothing to do with EI. It's controlled entirely by development.

Shadow detail is a function of exposure and EI, and cannot be changed by development.
- Leigh

That's what I was told: Exposure changes the shadows and development changes the highlights.

Fomapan 400 was not giving the stated speed on the box, because shadow detail was lacking.
That is a fact that Foma acknowledge in their technical data.
The same could be said for Shanghai. Maybe 50ASA, but not sure if the 4x5 is cut from the same master rolls as the 120 version.
You have to test a film/developer combination before doing any work of importance. So you can be reasonably sure that it will meet your requirements.

[IanBarber]

For those of us who don't have access to densitometers what's the easiest way to determine the true speed of the film we are using.

[Larry Gebhardt]

For those of us who don't have access to densitometers what's the easiest way to determine the true speed of the film we are using.

First determine your development time experimentally by printing, focusing on a mid grade paper like grade 2. If the contrast looks correct in the mid tones and highlights (ignore the shadows) you are there. If it's low contrast add 10%, and if it's too high subtract 10%. You should be using a normal contrast scene for this. Once your time is determined shoot the same scene at different film speeds. Pick a scene with normal contrast range and one that has details in the shadows. Outdoors I find most landscape scenes with trees or shrubs work well. I usually go box speed - 1.3 stops to box speed + .3 stops. For example FP4 is box 125, so shoot a sheet at 50, 64, 80, 100, 125, 160. Then develop at the time you determined earlier. Evaluate your negatives and choose the one that has recorded the shadow detail and isn't showing major blank areas. I find the best way is to print them and adjust the exposure time for your mid tones and keeping the contrast at grade 2. Each will require slightly different times. Pick the one with full detail with the fastest speed - that is your speed.

My results usually come out in the range of developing 10% less than the Xtol times and with a speed of -1 to -2/3 of a stop. Since I like slightly more open shadows I round down.

[IanBarber]

First determine your development time experimentally by printing, focusing on a mid grade paper like grade 2. If the contrast looks correct in the mid tones and highlights (ignore the shadows) you are there. If it's low contrast add 10%, and if it's too high subtract 10%. You should be using a normal contrast scene for this. Once your time is determined shoot the same scene at different film speeds. Pick a scene with normal contrast range and one that has details in the shadows. Outdoors I find most landscape scenes with trees or shrubs work well. I usually go box speed - 1.3 stops to box speed + .3 stops. For example FP4 is box 125, so shoot a sheet at 50, 64, 80, 100, 125, 160. Then develop at the time you determined earlier. Evaluate your negatives and choose the one that has recorded the shadow detail and isn't showing major blank areas. I find the best way is to print them and adjust the exposure time for your mid tones and keeping the contrast at grade 2. Each will require slightly different times. Pick the one with full detail with the fastest speed - that is your speed.

My results usually come out in the range of developing 10% less than the Xtol times and with a speed of -1 to -2/3 of a stop. Since I like slightly more open shadows I round down.

Thanks Larry, I shall try that and see how the results turn out

[Pere Casals]

For those of us who don't have access to densitometers what's the easiest way to determine the true speed of the film we are using.

Adding to what Larry pointed, You have a densitometer, just scan raw your negative alongside a ($7) Stouffer T2115 density wedge, you can check what grey intrevals are in an step of the Stouffer.

Also when you expose a test scene you may writte down how underexposed are your different shadows, just use the spot meter of a DSLR/SLR for example. Then with the Scanner+Stouffer densitometer you find what shadows have 0.1D over Fog+Base (unexposed film areas, interframe separation or example). Those areas in +0.1D are in the "m" speed point, so underexposed 3.3 stops from "true speed".

So correct for the "true speed" you were guessing. If you had the meter at ISO 100 but shadows at +0.1D were metered -2.3D only... then you have to correct the true speed by 1 full stop, if you use ISO 50 then those shadows with +0.1D density would instead have been metered 3.3 underexposed, which is the right setting for the true speed.

Just: when your true speed is correct then -3.3 stop shadows have 0.1D density over base+fog (fog+base = not exposed negative areas). If not, correct your "true speed".

If you want your exposure calculations based in "true speed" then you have to target -3.3 at +0.1D.

You can perfectly use any personal speed, but... what advantage has using true speeds ?

If you use always true speeds you will have a way more consistent metering across a range of different films/processings, if not with every film/processing you need a different rule wich is overcomed by using a "personal speed" (EI) for each film/processing, also not bad.

Absolutely this is a personal choice, some people like a more technical approach and some people prefer a practical way and going forward. Both kinds of people may make great art or nothing worth. The way you meter is not related to the work quality. For example AA was very technical and a great artist, but Karsh developed by inspection, and also he was a great artist.

Some people listen a soprano while watching the spectral domain to "see" the voice ormanentation. They may be sick or they may understand better the voice, this is what we are debating about film speed :)

186694

[Doremus Scudder]

For those of us who don't have access to densitometers what's the easiest way to determine the true speed of the film we are using.

Go back and read my post, Ian!

[Drew Wiley]

Here's one of the main flaws in all this "real film speed" talk : You're measuring it based upon a threshold value above fbf. Well, airplanes also have their own kind of fbf taking off and clearing the runway. But they don't all take the same angle of trajectory to get to cruising altitude. "Straight line" films have one kind of trajectory; long-toe films, another; many films are somewhere in between. Lith film is almost like a helicopter that can go straight up once it is started. All of this affects your very definition of film speed. No cut-and-dried generic formula can do that. And all of these can be somewhat modified by development regimen.

[Pere Casals]

Here's one of the main flaws...

The flaw is not explaining how true film speed is calculated...

This is a number, tell me, how do we caculate it?

[Drew Wiley]

Why bother if it doesn't describe how gradation is actually rendered? Don't we all tend to take advertised box speed, maybe cut in half, then slowly work our way up to find what is appropriate to our own needs? But all the major manufacturers have tech sheets or web pages with their own densitometer curves relative to recommended developers or times. That should give a clue where to start, along with other people's experience.

[Pere Casals]

Why bother if it doesn't describe how gradation is actually rendered?

Of course with some try/error cycles we may solve it !!! We use a personal EI that accounts for our metering style, and that's all... I fully agree...

Anyway with the true speed calculation for a film/processing we also find:

> The Contrast Index and a good guess for the paper grade. We have the gradation.

> Exactly what shadows will be lost and what shadows will be damaged in the scene, from spot metering.

> What highlight latitude we have and what footprint in the glares. (we have the curve, so the shoulder shape)

> The toe and shoulder shapes also tells what we'll find in the printing process, if we are experimented in handling graphs.


Graphs in Datasheets are useful, specially those from kodak, if we use a processing described in the kodak graphs then we only need to understand how the graphs can be used in practice, amazingly not many photographers are able to translate an spot metering in the scene to lux·second in the graphs, me I've learned that recently.
___


OP: "True film speed" vs just developing the film more?

This has an easy answer:

"True film speed" has a 3.3 stops latitude in the shadows, while "just developing the film more" increases contrast but it does not substiantally allow to record deeper shadows beyond what a the regular development time with same developer would obtain.

So if a "true speed" ISO 100 TMX is exposed at EI 400 then we won't have the regular 3.3 latitude in the shadows, but only 1.3 stops from the meter point if metering at EI 400, or a bit more from some small effect of the overdevelopment in the true speed.


"Developing the film more" essentially increases contrast, making an underexposed negative more printable, without improving much the "true speed" for the shadows.

[Bill Burk]

Pere, you know when you write 3.3 that you are rounding, right? It’s ok with me if you write that way if you occasionally acknowledge you are rounding for expedience but that it’s truly 3 1/3

[Pere Casals]

Bill, the true speed formula makes the meter aim to exactly x10 the exposure in the m speed point, this is exact. If we vary development then we have to calculate the true speed again making the meter aim again to x10 the exposure in the new m point.

The m point calculation has tight tolerances,
The box speed can be rounded to a standard speed, but the true speed is very well defined.

[Bill Burk]

10 times is exact. The translation to f/stops is three and a third.

It's a very minor point I am making, that 3.3 does not equal 3 1/3 because it is rounding a third to the tenths decimal place, losing a few hundredths in the rounding.

I don't even mind that you are rounding, just want you to be aware that you rounding in case you didn't know and are relying on 3.3 being exact.

Over on the logarithm side, .3 is one f/stop exactly. So there are times and places where you will be looking at .3 and it will be exact.

[Bernard_L]

Been reading through this thread and there are a couple of things I don't get.

- The 3.3 thing. Looking a the plot provided by Pere Casals in post #6, and the two points defining the ISO speed, the Delta(logH) is 1.3. Since log10(2)=0.30103, and rounding off to 0.3 for the value of an f-stop in a log10 scale, the Delta(logH) is 4.333 f-stops, which I'll boldly round off to 4.3. As much as I find the 0.03" round-off from 4.333 acceptable, that is definitely not 3.3, as has been repeated through the 7 pages of the thread.

- A trivial mistake, a typo shall we say; so why do I raise such a fuss? Because my first reaction was to check the relation of the upper point with the meter indication. Hmm, let's see, the speed point (sometimes B+F+0.1, sometimes more complicated but essentially the same) is supposed to be ZI in zone system language; so (I'm still with the 3.3), the upper point would be zone 1+3.3=ZIV.3 Not ZV? Alarm flag raised. Then I went back to simple arithmetic, 1.3/0.3=??
So the upper point of the ISO triangle is ZV.3, not ZV?? Maybe. Maybe not.

- Relation with lightmeters. The plot in post #6 has a horinzontal axis in logH, where presumably H is lux-seconds; ditto for the definition of ISO/ASA speed in the wikipedia article
S=0.8.lx.s/Hm
Since Pere Casals recommends reading BTZS, but I don't have it readily available, I read through the 5 articles on sensitometry on the btzs.org site, especially http://btzs.org/Articles/Sensitometry%20Part%204.pdf. I see various graphs, sometimes "relative log exposure", sometimes unlabeled...
Problem is: like most of ordinary folks, I do not have an NBS-traceable lightmeter calibrated in lux, or a calibrated sensitometer calibrated in lux.sec; I do have several photographic light-meters, with dials in f-stops, shutter speed, and ASA/ISO.
Question: how do I connect my measurements with all the nice plots? In other words: assuming I use all the proper procedures, standard developer, etc; I measure and expose a gray card, develop, where is it going to fall? And, pleeez, do not derail the discussion about 18% vs 12%: that is irrelevant because in the previous sentence I could have replaced gray card by white paper: the resulting film exposure would remain identical.

I had so far assumed that he "gray card" falls on ZV. Didn't you?

The articles by Phil Davies do not shed any more light. In Part_4 (link above) at Figure 5, an ASA/ISO scale appears out of nowhere under the (un-labeled) logH scale. Here is my take on what Phil Davies does: the "ASA triangle" selects the curve (dev time) with the correct contrast. He then assumes that you simultaneously achieve the nominal ASA/ISO speed. And what if you were to follow that procedure with a speed-losing developer? You would happily declare box speed has been achieved as soon as theh ASA contrast is obtained. And I still don't know where a metered uniform surface will fall on the logH-D curve.

Bottom Lines.
The Negative (A.Adams) and The New Zone System Manual (White, Zakia, Lorenz) appeat to implicitly assume that, under nominal conditions, a metered uniform surface will be exposed Zone_V
But the clearest indication comes from Controls in Black and White Photography (R.J.Henry), highly recommended. See atached pdf file. Emphasis added by me.

- Point M defines the speed point.
- Point N, 1.3 above point M in logH (4.3 stops) is used only to achieve the standard contrast index.
- If a uniform surface is metered, the film exposure will be ZV, 4 stops above point M (not 3.3, not 4.3)

[Pere Casals]

10 times is exact. The translation to f/stops is three and a third.
It's a very minor point I am making, that 3.3 does not equal 3 1/3 because it is rounding a third to the tenths decimal place, losing a few hundredths in the rounding.
I don't even mind that you are rounding, just want you to be aware that you rounding in case you didn't know and are relying on 3.3 being exact.
Over on the logarithm side, .3 is one f/stop exactly. So there are times and places where you will be looking at .3 and it will be exact.

Yes, x10 is what is the exact definition... from 3.3 to 3 1/3 we have a 0.033... difference

[Pere Casals]

- The 3.3 thing. Looking a the plot provided by Pere Casals in post #6, and the two points defining the ISO speed, the Delta(logH) is 1.3. Since log10(2)=0.30103, and rounding off to 0.3 for the value of an f-stop in a log10 scale, the Delta(logH) is 4.333 f-stops, which I'll boldly round off to 4.3. As much as I find the 0.03" round-off from 4.333 acceptable, that is definitely not 3.3, as has been repeated through the 7 pages of the thread.

Bernard, the 3.3 vs 4.3 issue comes from the 1960 speed change specified in the American ASA PH2.5-1960 standard.

In 1960 Box speeds were doubled without any manufacturing changes in the film. If you read pre-1960 literature you have to be aware that there you have sensitometric calculations for 1/2 of the today's box speeds, this explains the 3.3 to 4.3 difference. Today (since 1960) it is 3.3.

(see https://en.wikipedia.org/wiki/Film_speed#DIN, section 1.1.4)



And what if you were to follow that procedure with a speed-losing developer?

In this case you have a different true speed, the film datasheet speed calculation has to say the developer used, if nothing said a full speed developer that is D-76 equivalent is assumed. Then you add the effect of the speed-losing developer to your metering, or you have to calibrate your film/processing combo to find your true speed.

For example Adox CMS 20 requires an special developer, speed is specified with Adotech II developer... Kodak shows in datasheet teh curves with H units in log lux·seconds with a certain developer... better specified it is impossible...


So the upper point of the ISO triangle is ZV.3, not ZV?? Maybe. Maybe not.

That point of the ISO triangle is not the meter point, remember the 1960 speed change. A zone is not a particular exposure, it is 1 stop wide, so a range of exposures. Meter aims to the center of the Z-V.



- Relation with lightmeters.

See: Table 3. Exposure value vs. luminance (ISO 100, K = 12.5) and illuminance (ISO 100, C = 250) here: https://en.wikipedia.org/wiki/Exposure_value

This wiki article has detailed explanation of all calculations and concepts, and the margin of some constants.

From the tabulated EV 100, (ISO 100 in the meter) we of course may find the light power for any rated speed.

[Bernard_L]

Pere, that is what you state in post #61.

Bill, the true speed formula makes the meter aim to exactly x10 the exposure in the m speed point, this is exact.
[10x = 3.33 stops]

And here is what R.J.Henry wrote in 1978; presumably he was aware of the 1960 revision of the ASA standard. In fact, and being a precise person, he refers in his Glossary to ANSI PH2.5-1972.

The meter will give you an exposure for Zone V in the Zone System assuming your meter is correct and the manufacturer’s ASA rating is correct for your set-up, including subsequent development.
(...)
ASA film speed is determined from point M on the curve which, as previously stated, is where the lm D is 0. 1 above B + f. If the manufacturer’s rating which was set in the meter was correct for our meter, procedure, etc, then point M would fall exactly 4 stops (relative log H of 1.2) lower than the point on the graph corresponding to the Zone V exposure.

This is the main point. Now every reader has the information available, and I will not argue further. The other points are of lesser importance, or derive from the main point.

[Luis-F-S]

What difference does it make if you never go and take photos because you’re glued to the computer!

[Bill Burk]

All agree then, in this thread where you see 3.3 or 4.3 in terms of stops, it is shorthand for 3.33 and 4.33 (because unless stated in fractions you have to round off the irrational numbers somewhere).

[Bill Burk]

As others have written ASA triangle defines the contrast and the base goes beyond the meter point.

ASA triangle base is 1.3 log which is 4.33 stops but not used for the metered point.

Zone System departs from ASA by calling Zone V 4 stops over Zone I and is 4 instead of 3.33 stops. That’s the Zone System metered point. Between Zone System and ASA the difference is 0.2 log which in stops is 0.66

The direction and amount almost entirely explains why Zone System testing nearly always results in “one stop” less than ASA speed (in many places people say it is two-third stop difference between the two systems).

[Pere Casals]

And here is what R.J.Henry wrote in 1978; presumably he was aware of the 1960 revision of the ASA standard. In fact, and being a precise person, he refers in his Glossary to ANSI PH2.5-1972.
This is the main point. Now every reader has the information available, and I will not argue further. The other points are of lesser importance, or derive from the main point.


Bernard, we have to assume that the "on film" density in Zone V changed in 1960, by one step.

We have to understand the concept of the 1960 change. Pre 1960 epoch metering was worse, and it was considered that film had 1 stop additional safety factor.

With better metering and removing the 1 stop safety people obtained better images, because they had an additional stop for the shutter or for DOF, and labs received better exposed film.

Some Fine Art photographers were metering accurately by 1960, so for them this was an imposed change they were not asking, thus creating an incredible ammount of confusion.

If we learn what's true speed then discussing that is irrelevant...


But if I was Fine Art photographer in 1961 (just after speed change) I would had next choices:

1) I divide box speed by 2 and I do the same, to hell with ASA guys.

2) Now (1961) meter is aiming to Z-IV, so I place in Z-VI to what in 1959 I was placing in Z-V.

3) I was placing (1959) deep shadows in Z-II or III now (1961) I place shadows in Z-III or IV.


If we want to use the pre-1960 way we are free to do it, and we can consider that meters aim Z-IV so we have to overexpose 1 stop, or we can consider detail in the low zones is now lower. We to the same at the end.


Both ways work, to me the meter aims to Z-V and I adapt my metering to that, for the sake of conceptual simplicity.

If someone wants the meter aiming Z-IV then he also will adapt: at the end we have the same exposure.

The controversy comes from not explaning well what one is doing, but anyway this is confusion was generated by the 1960 speed change, and we are in 2019.

But ZS and the speed change were for the mainstream so IMHO best is that "Fine Art" makes the adaptation to the "removed safety factor", this is 2019 yet, and the change was 59 years ago...

[Bill Burk]

What difference does it make if you never go and take photos because you’re glued to the computer!


Good point. I don’t even have my Grafmatics loaded right now. I’ll load up today. In my booklet, I make a similar point.

If you can follow the logic so far, you do not need to do Zone System testing. Shoot now at ASA speed minus two-thirds of a stop. So shoot 400 speed film at 250. You haven’t developed the film yet, so the N times can remain undefined until later when you come back from the trip of your lifetime.

That’s if you use Zone System style metering. If you are using a different metering method like incident reading, you might get readings to agree if you use ASA speed for the more mainstream metering techniques

[Bill Burk]

Bernard, we have to assume that the "on film" density in Zone V changed in 1960, by one step.

We have to understand the concept of the 1960 change. Pre 1960 epoch metering was worse, and it was considered that film had 1 stop additional safety factor.

With better metering and removing the 1 stop safety people obtained betters images, because they had an additional stop for the shutter or for DOF, and labs received better exposed film.

Some Fine Art photographers were metering accurately by 1960, so for them this was an imposed change they were not asking, thus creating an incredible ammount of confusion.

If we learn what's true speed then discussing that is irrelevant...


But if I was Fine Art photographer in 1961 (just after speed change) I would had next choices:

1) I divide box speed by 2 and I do the same, to hell with ASA guys....

This was a great post. I’d say the first choice was always the best

[Pere Casals]

I’d say the first choice was always the best

Bill, this is best for understanding the metering of classic photogarphers in the pre-1960 literature... sure... And also sure this is still a popular and effective way !!!

To me it's the same if the prime 0º meridian is in Greenwich or in Alexandria, IMHO the important thing is that Eratosthenes in 276 BCE made the first map of the world incorporating parallels and meridians, so we know how a map has to be.

IMHO considering ZS has the meter aimed to Z-IV or to Z-V has the same practical result from adaptation. The IV version is more historically consistent with Fine Art works, but IMHO adapting to the Z-V version should be preferred because it's more consistent with mainstream photography that saw the 1960 change as a safety factor change.

I ask, did Ansel Adams said something about that ? did he accept the box speed change as a safety factor change ? I don't know if he said something, but if not then IMHO he considered the speed change was only for a safety factor change, and he agreed to no modify the zones...

Just my interpretation...

[Bill Burk]

I don't feel comfortable calling it Z-IV, just sounds funny (you're not wrong, it's just an adjustment I don't feel good with). I always think of Bruce Barnbaum when I see Z-IV, it is his shadow placement.

Plain and simple to me, meters have always been Z-V and the Zone System is a different model than ASA so they don't agree.

They differ by 2/3 stop (ZS users could use EI 250 for ASA 400 film). In the past they differed by 1/3 stop the other way (ZS users would have used EI 250 for old same film that was ASA 200 pre-1960).

Ansel Adams thought the K factor was a meter manufacturer's deception which accounted for the difference. He was always saying the Zone System speed is a film's true speed. He wanted to claim a true speed because he was using spotmeters to evaluate specific subject luminances and he wanted a direct tie between that and his film.

If I sat down with him at a rock overlooking a river, though, I would not have talked of this stuff. I'd be talking about the way the water moves.

Same as if I were to go hiking with DREW WILEY... I wouldn't talk about this. We'd be too busy watching the clouds.

[Doremus Scudder]

While this thread is interesting and the discussion lively, I really believe that "true film speed" is largely irrelevant. The OP is just confused the the variety of ways people treat a specific film; this E.I. or that one...

More experienced photographers have figured out that ISO standards are just a way to test and rate films relative to each other under controlled conditions and that the ISO conditions and the speed derived therefrom don't usually apply for practical situations, they are there for comparison. This is especially true for black-and-white materials, since development is such an important factor in the whole scenario. For color, development is more-or-less standardized, but metering and personal preferences are still large enough factors that a personal E.I. often gives better results than "box speed."

Anyone who's worked with the Zone System for a while quickly finds out that Zone V isn't middle grey and that the distance between Zones is not a fixed change in density.

All that really matters is that we find a way to get the shadow detail we need for whatever way we meter, i.e., find a personal E.I., and find a development time (or times for Zonies) that gives us the highlight density range in our negatives that allow us to print the image well.

I use the Zone System and a spot meter, and have tested for my personal E.I. for a number of films and development schemes doing the usual Zone System tests (although without a densitometer, a lá Minor White et al.). However, I likely could have arrived at my personal E.I.s by simply bracketing a bit, changing development time as needed and keeping good field notes. I'll likely do just that for the next film/developer I try out.

Film speed for me is simply the minimum exposure I can get away with to get the shadow detail I want and the development time that gives me highlights that I can print easily. There are a ton of refinements on this rather simple formula (e.g., learning a film's toe shape and placing lower or higher to get more or less shadow separation, or increasing local contrast by underdeveloping and printing on a high contrast grade, or overdeveloping to get mid-tone separation, knowing that you'll have to dodge and burn like hell when you try to print...), but the basics are easy and all that's needed to get really good exposure and development is a camera, film, some photo paper and a rudimentary understanding of how photo materials work.

Once we realize that ISO is there as a standard of comparison, much like the mileage ratings for new cars (who ever gets that kind of mileage anyway?), and that we will likely need to use a different setting to get good results, we suddenly don't feel like we're transgressing when changing that film speed dial. Zeroing in on an E.I. and a development time is pretty easy really, once we do that. Who cares about "true film speed"?

Best,

Doremus

[Pere Casals]

I really believe that "true film speed" is largely irrelevant.

Doremus, me I think the counter, to me true speed of a film/processing is the absolute reference to compare things. By knowing the true speed and the spot meter I know exactly how far is a shadow from the 'm' speed point, and what density I'll have i the highlights in the negative to know how difficult would be printing that. All what I need. Mids are always in the linear part or the curve, so by knowing what happens in the extremes we have all, isn't it ?

[Drew Wiley]

Pere- how on earth can anything like this be an absolute standard unless the actual gradient is consistently straight? Extrapolating between points on the toe while the rest sags in between might be an acceptable as a taxonomic convention for film speed, but it doesn't describe tonal separation itself down there realistically at all. And it does seem to depend on what the given manufacturer decides is relevant, which is not necessarily consistent between brands, or consistent with our own specific needs. .... And Bill, yes indeed! I hate gear talk on the trail. Bring any camera you like. Makes no difference to me whether it's a cell phone or a wet plate 16x20, or no camera at all. I'll bring what I like. This is the kind of place for shop talk. But once I'm outdoors, I'm really outdoors.

[Pere Casals]

Pere- how on earth can anything like this be an absolute standard unless the actual gradient is consistently straight?

Drew, you like linear films, so you won't have any problem...

Using the true speed as a reference all films/process behave mostly the same from -2.5 to +3.0, this is linearly with no tonal compression, in that range BW films are consistently straight. We have certain character in the toe/shoulder/swept.... but film character is not covered by exposure systems.

So from the to the toe/shoulder/upswet we have a character, but still true speed value and "m" point are the principal parameters, any exposure system ends using that more or less evidently... isn't it?

[Drew Wiley]

Thank you, Pere - But I use a variety of films. And even ones that take off the runway rather quickly like T-Max change their character in certain developers. I always visualize the actual curve in my head when making shadow placements. It's become almost second-nature by now for any number of films. In the lab for nitpicky work like color separation negatives, I keep on hand a whole suite of densitometer plots for sake of precise results. In the field, there is often no time for that.

[Pere Casals]

Drew... but if using the true speed of film/process,. if with a film you place a shadow at -2 then with another film you also will place that shadow at -2, isn't it?
What would you vary, a 0.5 stop?

[Alan Klein]

Since I send my 120 film used for landscapes out to a pro lab, I shoot at box speed and bracket +1 and -1 for both Velvia 50 and Tmax 100. Seems to work although I'm open to recommendations.

[Pere Casals]

box speed and bracket +1 and -1 for both Velvia 50 and Tmax 100. Seems to work although I'm open to recommendations.

All depends on how accurate you meter and how precise you expose (shutter tester). Just see from the results, see how many times the bracketed images have a benefit. I would perhaps do only the +1 bracketing for TMX and the -1 bracketing for Velvia, but IMHO practical results you obtain should guide you.

[Doremus Scudder]

Doremus, me I think the counter, to me true speed of a film/processing is the absolute reference to compare things. By knowing the true speed and the spot meter I know exactly how far is a shadow from the 'm' speed point, and what density I'll have i the highlights in the negative to know how difficult would be printing that. All what I need. Mids are always in the linear part or the curve, so by knowing what happens in the extremes we have all, isn't it ?



... but IMHO practical results you obtain should guide you.

Pere,

You're contradicting yourself! :)

Two observations: First, sure, "true film speed" is important, but Kodak and Ilford have figured that out for me and stamped it on the box: ISO XXX. I don't need to test for ISO. I need to test for the variables in my workflow. Maybe I meter differently than the ISO guys, or maybe my meter is a bit off so that my Zone III isn't really... But, if I adjust me E.I. to get the Zone III I need, then I've solved the problem. I don't really give a hoot about how far my Zone III (or any other zone for that matter) is from the "m" speed point. I only need to know that I've got a rating for any particular film that gives me the exposure in the shadows I need. Practical experience guiding me here :)

And, if all films had the same curve, we could just use the published ISO to compare them. It's the differences in film characteristics that often determine how we finally decide to expose. As I mentioned, I'll often play with exposure on 320 Tri-X to put different parts of the scene in the straight-line portion of the curve; overexpose to get the shadows up off the toe, underexpose a bit to keep some not-very separated shadow detail, but get the mids on the upswept part of the curve. etc. Here, E.I. is relative to where we want to place the range of luminances in the subject on the film curve. "M" isn't going to help me there.

There are a ton of other variables that inevitably creep in when working in the field that you just can't control all that well. However, practical experience often gives us at least an idea of what to adjust to come up with a negative that will make a good print. That's all I really need. I don't have to have an ISO calibrated meter or a densitometer, plot graphs, etc. My prints tell me whether I've succeeded or failed and what I need to do to improve.

Best,

Doremus

[Pere Casals]

Pere,
You're contradicting yourself! :)


Well, I also find funny discussing aganist myself !! :)



but Kodak and Ilford have figured that out for me and stamped it on the box: ISO XXX. I don't need to test for ISO. I need to test for the variables in my workflow. Maybe I meter differently than the ISO guys, or maybe my meter is a bit off so that my Zone III isn't really...

Of course Box speed may not be the true speed of your film/process, and your metering style may have any character. So if you put in the same bag your film/process speed, your metering and your shutter accuracy then you have all in single factor and a safety factor, just knowing how each "personal zone" looks under each +/-N you are done...

I've no bad critique with that way, it's the perfect one for most needs, but you may admit that at the end (indirectly) your reference is the actual true speed of your film/process. You know perfectly in what "personal zone" you have tonal compression and in what you have lost all detail, so you find the true speed point in an indirect way.



As I mentioned, I'll often play with exposure on 320 Tri-X to put different parts of the scene in the straight-line portion of the curve; overexpose to get the shadows up off the toe, underexpose a bit to keep some not-very separated shadow detail, but get the mids on the upswept part of the curve. etc. Here, E.I. is relative to where we want to place the range of luminances in the subject on the film curve. "M" isn't going to help me there.

Ok, but this is beyond exposure systems. Zone System teaches standard zones without asking if you have the TXP shoulder (depending on processing) or a linear TMX end.

It is said that TMX requires an accurate exposure, this is true because if overexposing then the highlights are unprintable because of excessive density so a "somewhat" thin negative is less risky, buy TMX it's easy to expose, beyond "m" speed point you have a line so there is no tonal manipulation from the negative, we delay tonal management to the printing process.

What is more complicated is what you explain... this is knowing the curve of your film/process and making the tonal management in the film exposure, this allows controlling the rendering of shadings (volumes), which I find essential in portraiture.

...but you may want or not to know what's your true speed and by accurately metering to be aware if a shadows is at 1/2 stop of it or at one stop far, alternatively you realize that from testing.

Me I prefer having the family of curves calibrating my process, from the spot reading I know if I'm in the shoulder or in the toe, and by the bending of the curve I know if I've a tonal expansion or compression there...

It's a personal preference, but also I want graphs more than the average amateur because I'm messing with DIY emulsions that I try to shape from mixtures of different speed batches and from layering two different emulsions on the plate, placing the faster one in the top.

Also I find calibrations very practical for BW slides, what I'm to do from now is calibrating the reversal processes by exposing several contact copies of the stouffer and using several 1st development times for each strip, then I take the Provia curve in the fuji datasheet and compare, I just pick the curve that matches the Provia gradient, and as both my graphs and fuji graphs have lux·second units then I get the real speed I've to use. I know how to expose provias so I nail the BW slides from any BW film in the first chance.

Well, sensitometry may be essential or irrelevant, it depends on what we are doing and if we love or we hate graphs !!!!

[Drew Wiley]

Bracket? Why??? That's what light meters are for, or else a big credit card limit if you shoot 8x10! - provided nothing moves between shots! ... So here's my point of view, Pere (which might or might not apply to other people) : I shoot both color and black and white, so think of a "Middle Gray" or Zone 5 as the conspicuous little red triangle on my spot meter corresponding to an 18% gray card reading (I realize that gray cards differ somewhat, and the factory calibration of meters is a bit more sophisticated, but this is the hypothetical center at least). But going down the slope from there, a few "straight line" 200 films would cleanly resolve 5 stops down into the shadows (-5 + Zone 0), films like TMax -4 (Zone 1), films like FP4 and ACROS -3 (Zone 2, ala AA doctrine), Pan F only -2 (Zone 3). I'm rounding to full stops for sake of simplifying the conversation. I have no idea what kind of film Barnbaum had in mind by ignoring most of the shadow range. Likewise, films differ with respect to where they shoulder out above Middle Grey.
So a generic "Speed Point" at minus 3-1/3 just doesn't make sense for me. Like I already implied, different kinds of airplanes lift off the runway at different angles of trajectory. Then there is the fact you mention about the necessity for a family of curves for any given film/developer combination. True indeed. Not only is the overall contrast (gamma) affected by this, but the nature of the toe itself. I choose films and expose and develop them with all this in mind. What I rarely do is compensating or "minus" development.

[Pere Casals]

a few "straight line" 200 films would cleanly resolve 5 stops down into the shadows (-5 + Zone 0),

Drew, what films/development ?

Think that from film speed definition, all films have 0.10D (over base and fog) at -3.3 stop in N conditions... You place 1.7 stops in 0.1D range over base+fod... can this be clean ?

[Drew Wiley]

Think it over, Pere. That -3.3 over fbf doesn't tell you much of value. It's just a convention at best. Films truly differ. But since you ask about realistic minus 5, the late Bergger 200 would do it, and Super XX before that. Fomapan 200 is the only current film I can think of, but it has some severe idiosyncrasies. Of course, this assumed precise shadow metering. I do minus 4 with TMX and TMY rather often, at least if scene contrast range if strong enough to warrant it. Doing it this way versus tonal compression can lend some real snap into prints. You should also note how TMax films have almost no base fog in sheet version. So yeah, 0.1 above is completely usable in that particular case, provided one knows an appropriate development regimen. But I always joke about this being for adults - those who own a spot meter and knows how to use it. But if skating on thin ice isn't your sport, you can place your deepest shadow values a bit higher.

[Pere Casals]

Drew, this is impossible...
You are saying that with bergger 200 you can expose for a subject under sunlight at f/16 and 1/8000s and still get a clean image.
this is wrong!

[Bill Burk]

Haa, no. With a 200 speed film, EI 125. Say a sunny 16 shot usually meters with shadow placed on Zone III as 125th f/16. Drew's saying he can place the shadow on Zone I (expose at 500th f/16).

[Pere Casals]

Well, this was Z-0, in fact. We can place a shadow there if we want, but we can't expect to se detail in it...

Just from datasheet Panchro 400 starts building density in the toe at -4 stops from meter, in the -4 to -5 interval nothing is recorded, but from -4 and up it records compressed detail. We may have good detail in Z-II, but to overcome uncertainties from metering and exposure this is Z-III in practice, in special if we may want a -N development...

But well, if Drew rates Bergger Panchro 400 at 200, then he is right in that from -5 to -4 detail is also recorded, because the thing shifts 1 stop. If he was speaking in the 1959 nomenclature then he was right, but in post 1961 words we have detail from -4, good detail from -3, and safe detail from -2.

So it seems we are in the Back To The Future movie :)

Bergger provides curves for 3 recommended developers, http://bergger.com/media/wysiwyg/Fiches_techniques/Pancro400_en.pdf,

186969

https://www.largeformatphotography.info/forum/showthread.php?150168-So-I-m-looking-at-film-prices&p=1480477&viewfull=1#post1480477

Here Paul posted this sample, showing highlight separation from film shoulder, anyway it would be interesting to know the spot metering in the highlights ...the shoulder footprint is only seen beyond 2.0D, so where well +2 overexposed, D-76 delivers a less shouldered shape than pyro devs... from datasheet info.

https://c1.staticflickr.com/1/883/42027098225_31da866034_b.jpg

Just I'd like to show my view about how exploring sensitometry of a film/process allows to understand its nature, this would help to learn how to get the aesthetic practical exploit we may want. Bending a curve in Ps is straight, but mastering the tonal curve in a pure optical process requires proficiency. Yes, we may use any well known recipe, but personally I find sensitometry useful to me to learn how things work. Probably when I'm more experimented I will need less the graphs...

[Drew Wiley]

Pere, you are obviously unfamiliar with the very significant distinction between ole straight line 200 color separation films (e.g, Super XX, Bergger 200) and something like Bergger Panchro 400 which bears no relation to those discontinued products other than a marketing brand name, and which has a substantial toe. Fomapan 200 is the only thing currently on the market with a straight line that deep into the shadows, but it's nowhere near true 200 speed. Don't tell me it can't be done, or that I need to overexpose the neg to get it up on the straight line. If you've paid attention to anything I've said on this thread, it is the benefit of using the entire curve of an appropriate film for high contrast work rather than over-exposing, under-developing, and scrunching the sandwich. I do it that way all the time with excellent results in the print. But of course, one cannot conveniently carry a lot of different films at the same time, especially 8x10 holders. One has to strategize and anticipate conditions somewhat.

[Pere Casals]

using the entire curve of an appropriate film for high contrast work rather than over-exposing, under-developing, and scrunching the sandwich.

Drew, anyway, the exposure requires at least the minimal ammount that is to record the shadows with the detail we want, so it may not be a way to not overexpose certain area if wanting certain shadows well recorded. Then... what we can do if we have important areas very overexposed ? If we develop normally then some densities will be sky rocketing... woudn't we require a compensating development ?

Tell me what's "using the entire curve" if you have a 8 stops range in the scene...

[Drew Wiley]

Most b&w films handle 8 stops of range just fine; that's probably why all that old Zone talk standardized on a dynamic range that size. A shorter scene contrast range obviously warrants more development. But what about a contrast range significantly greater than 8 stops? Sure, you can overexpose and underdevelop and, within reason, accommodate the endpoints in the sum sandwich. But what will be the cost to gradation and microtonality in between? Merely printing on a harder paper grade only partially solves the issue, because you've probably altered the curve shape of the film somewhat by underdevelopment, and not just overall contrast gamma. So, sometimes, the better option would be to just use a film with a longer potential scale to begin with. If more range happens to be realistic in the shadows, why not use it? Why be religiously stuck on some inflexible rote mantra that shadow texture has to be placed on Z 2 or 3 or 4 or whatever? - depending on what guru you place blind trust in.

[interneg]

Worth noting too that Kodak's idea of 'N' development time translates to placing 8 stops on an average G-2 paper exposure scale with a diffusion enlarger (albeit, there are a few slight issues with this as it does assume a particular amount of flare, I recall).

[Pere Casals]

Most b&w films handle 8 stops of range just fine;

Yes, but if not making a compensating development then you get a density interval of some 2.6D, from some 0.2D to some 2.8D, so you we have extensive troubles to get a sound print. 2.8D is funny to print...

[Pere Casals]

Worth noting too that Kodak's idea of 'N' development time translates to placing 8 stops on an average G-2 paper exposure scale with a diffusion enlarger (albeit, there are a few slight issues with this as it does assume a minimum of flare, I recall).

Interneg, a 2.8D negative with grade 2, with no extensive manipulation?

[Drew Wiley]

Pere, you're guessing at all this. I'm not against flying by instruments; but sooner or later you have to try something other than a flight simulator.

[Pere Casals]

Pere, you're guessing at all this. I'm not against flying by instruments; but sooner or later you have to try something other than a flight simulator.

No guess, normal developement has a fixed density increase to a exposure amount, just check the kodak datasheets that are in real units, anyway with relative units (ilford) you arrive to the same.

This is a N-3 or beyond, and reaching 2.0D: https://www.flickr.com/photos/125592977@N05/28693688313/in/dateposted-public/

I had made a N I would had "smoke" from the negative...

[interneg]

Interneg, a 2.8D negative with grade 2, with no extensive manipulation?

It's not about that negative, it's simply a statement of what Kodak feel the 'correct' average development is. You'll generally get a little more camera flare on average with LF, but if you're contact printing, almost no flare at the printing stage, so it all events out somewhat.

Too often people get obsessed with opening shadows that should be dark...

[Bill Burk]

Interneg, a 2.8D negative with grade 2, with no extensive manipulation?

Interneg is a user name not what we are making.

You forget the average gradient is close to half. I imagine the aim is to print something like 1.3 density as highlight which is absolutely easy.

[Drew Wiley]

Then you have folks who want a negative to print well on both ordinary silver paper and some non-silver UV contact process. So that throws out some of the preconceptions too.

[Pere Casals]

Then you have folks who want a negative to print well on both ordinary silver paper and some non-silver UV contact process. So that throws out some of the preconceptions too.

This is solved with stain...

[Pere Casals]

Interneg is a user name not what we are making.

You forget the average gradient is close to half. I imagine the aim is to print something like 1.3 density as highlight which is absolutely easy.

With normal development each 3,75 stops then density rises additional 1.0D, so at 7.5 stops we are at 2.0D over B+F, so some 2.2D.

6 stops scene range we are at 1.6D + FB, so some 1.8D... IMHO this starts demanding a compression...

[Bill Burk]

Seven stops is 2.1 log H and roughly divided by two is 1.05 density.

Your example 3.75 stops x .3 log units per stop is 1.125 on the log H over the range of which your film density will grow about half... 0.56

I am simplifying by saying half while ASA gradient is 0.62 and some Zone System users call N somewhere in the neighborhood of 0.55

[Bill Burk]

Nice thing about what you’re doing Pere, since you’re making a computer program you only have to figure this all out once.

Haven’t talked much about flare, but the impact on the image is as if even straight toe film has a toe.

[Drew Wiley]

Pere - lots of those dual media types did not in fact employ staining developers. A few did; but older pyro formulas had a reputation for being unpredictable. We have more choices of them today. That's why a "thick negative", seriously overexposed, was espoused. But that strategy brought its own problems. The old thick-emulsion films (not to be confused with thick in the sense of over-developed) were more cooperative in certain respects than our current selection of basically thin emulsions. But they were a lot grainier too. And a lot of the anachronistic lingo and methodology of that era has become entrenched into Zone theory discussions, for better or worse. But even today, image stain can't do it all. We're lucky to have some excellent VC papers today that also help. But if you seriously overexpose, you can still get in trouble. Unsharp masking is another useful lasso to have at the rodeo. Gosh, the last couple of months I dug out some early overexposed negs and successfully reprinted them. The bigger problem was the dust marks and scratches of my early learning curve, when I was still loading film holders and even developing film in the furnace closet. Overall, what a headache! But it was worth it.

[neil poulsen]

If one uses the zone system, that is, if they expose for the shadows and develop for the highlights, then using ASA 200 as the film speed will work fine. (I use HP5, and my tests have always resulted in using an ASA of 200.)

On the other hand, if one uses sort of an average value for exposure, then I wonder if the box speed wouldn't be sufficient. (I don't really know, because I don't meter this way.)

I understood the zone system much better from reading The New Zone System Manual by Minor, Zakia, Lorentz. Ansel Adams explanation is puzzling for me, especially with his emphasis on Zone V.

[Pere Casals]

On the other hand, if one uses sort of an average value for exposure, then I wonder if the box speed wouldn't be sufficient. (I don't really know, because I don't meter this way.)

Neil, in that case all depends on how the scene is. With average metering, if we have snow around subject then we'll tend to underexpose, if we have a black background we'll tend to overexpose the subject...

but if it's a uniform scene, say a building in the shadow, then (with the ISO development) we'll get 0.62D +0.1D + Fog + Base. So around 0.92D average density.

If this exposure (box speed) is sufficient it would depend on how deep are the shadows, we know that at well metered -3.3 underexposure we will obtain 0.1D over fog+base, this is a very well defined reference point.



making a computer program

Thanks! Development is advancing nicely, it's my hope it would be useful...

[Drew Wiley]

Averaging is kinda like political polls. Sometimes they predict correctly, sometimes they sure as heck don't. And averaging bears quite different implications for color photography than for black and white, because you're concerned with what color hues saturate at a given exposure level, whereas in black and white work its a much longer gray scale. Earlier this afternoon I was out on the shoreline with color film for some nice light, and I knew exactly which foliage greens would correspond to middle gray, even though they were not gray in color at all. And I knew that the backlit fresh grass needed exposure one stop above that to look like the radiant color it was. But in black and white work, I could have placed the grass anywhere I wished relative to how I wanted the overall scene interpreted. I could underexpose it and develop strongly to emphasize highlight gradation, or I could conversely overexpose it to favor significant shadow gradation, just to mention two of many possible options. We make our own rules, and are free to change these rules from image to image. But that persistent little red triange in the middle of the meter does serve as a convenient reference point; so I'm certainly not surprised that AA standardized his conversation around Zone V.

[Pere Casals]

the backlit fresh grass needed exposure one stop above that to look like the radiant color it was.

Drew, of course one thing is sensitometry and another one is a practical shot.

All we know that "subject's color vs meter spectral sensitivity vs film spectral sensitivity vs filter" has an impact. And many other inaccuracies may follow.

Sensitometry simply explains how a medium-processing combo works, but we have other important factors, of course. Then we may start speaking about what an image has inside it...

[Drew Wiley]

Re-read what I posted, Pere. I was referring to cross-usage of meters between black and white photography and COLOR PHOTOGRAPHY, not just filter factors and peak meter sensitivity. If one does both, basing settings on the mid-point marking just makes sense. It makes sense for monochrome photography alone too. How else do we compare things in a quick easy manner? It was therefore convenient for AA and other to teach exposure methodology relative to 18% gray reflectance equalling Zone V, just like the center mark on every meter does, whether the film involved is color or black and white.

[Pere Casals]

Drew, IMHO what's the most important from ZS is visualization of the print from the zones in the scene. Many times we may not "see" how the image will be in fact, because on paper we may have a reduced dynamic range compared to the scene. If we select something in the scene then we have a visual reference...

In the other side the "true speed" says what density we'll have in the negative if we do a ISO normal development. We know that spots metered at -3.3 will have 0.1D density, while those metered at -/+0 will have 0.72D, both over base+fog.

...so I feel basics are quite easy.

[Drew Wiley]

The only problem with your "basics" is that it's based on an erroneous generalization, and only works, at that barely, if the target from which -3.3 is subtracted (in other words, Zone V) is a floating rather than fixed point of 18% gray. You're welcome to build an exposure model like that, but it wouldn't correspond to either the Zone System or typical meter usage. It's also easy to disprove using a densitometer with various real film options rather than a hypothetical stereotype. Just another straightjacket set of artificial rules that deserve to get broken.

[Bill Burk]

The ASA parameters define speed concretely at the 0.1 speed point. The distance to metered point and density there is not so spelled out. But by calculation confirmed with some tests, 10x is a reasonable approximation (Pere calls it 3.3 stops / I call it three and a third and we mean the same thing), and Pere gave density expectations that help confirm the contrast is reasonable.

But the density at the meter point is a confirming value, not a target.

[Drew Wiley]

Once again, that kind of model assumes that all planes take off the runway at around the same angle of trajectory, which they obviously don't. And yes, I realize that due to this, the lower part of the curve gets mathematically extrapolated a bit to make the formula fit. But that's right where we should be most concerned about the actual characteristics of the curve and not just the ASA convention, which blatantly differs from product to product anyway. Color films have less an issue in this respect because the toe and shoulder of the film are basically worthless; so the ASA ratings seem to be spot on relative to 18% gray. I would therefore contend that with black and white films, the ASA rating is as much a marketing tool as predictive of anything "concrete". Private label film can be even worse - the relabeled product rated at even high speed than the brand name master roll it was cut from. I've seen that several times. And I've sure as heck done enough densitometer plots of my own to know that minus 3-1/3 is far more hypothetical than real.

[Bill Burk]

I'm comfortable locking down where you meet ASA parameters at the 0.1 speed point.

At that point you're holding the rattler down on the ground by his head. He's not going to hurt you.

I'm not worried about the noise he makes at the other end.

Once you've got that, you can compare different developers and films. If the toe is specially long you can tell from the curve if there's another stop you can get out of it.

I know there's something magical about placing exposures as low as you can, so that you can have more of the negative density scale available in the mid to upper scale. I'm not so talented that I can use that to pictorial advantage. I prefer to put my pictures all on the straight line, so a film with a sharp toe fits my needs just fine. Generous exposure fits my needs just fine. But there are people who can feel it, sense it and use toe exposures to the advantage of the mid to upper tones. You can call it "micro tonality" but basically the idea is that the film has wavy curves and if you know where it is, and can put a bit of an upsweep in a person's face, it can put detail where it's most needed. Most people don't care about detail in the shadows. But they like detail in faces.

[Pere Casals]

Once again, that kind of model assumes that all planes take off the runway at around the same angle of trajectory, which they obviously don't.

Drew, single problem is inaccuracy in our side.

If you shot a Nikon F5 this is exact, because meter is a true scientific instrument, you meter TTL so glass transmission and flare is accounted. Then shutter is electronically re-adjusted automatically to be really exact, from long exposures to 1/8000.

We can meter/expose very accurately with a view camera, but it is not as easy. We may require a metering probe and a shutter tester.

With the Normal ISO processing it is true that a film may a have perticular curve, but we know that the calibration made by a good manufaturer is good.

Drew, just make a test, take fresh TMX and FP4+ rolls and an F5, use the F5 spot meter and shot an scene. You will find that -3.3 zones nail the 0.1D range and the -/+0 zones nail 0.72D, both over fog + base.

Me, I've tested it, and I found that it's like manufacturers and ISO norm say it has to be. If we vary processing, then we may calibrate the non ISO process or we may simply make some bracketings to see, both ways are good !!!

But let me reiterate that sensitometry is science, and ISO is industrial norms, so IMHO there is no discussion about that, it's about reading what says the norm.

[Drew Wiley]

TTL doesn't solve this kind of thing at all. It introduces other variables. For instance, incorrect filter factor readings. TTL meters certainly aren't "color blind". I've found Nikon TTL metering to be less dependable than handheld spot metering. Under certain circumstances one might use a Sinar film plane meter probe; but that's inconvenient in the field. Flare is pretty much a non-issue for me because I mostly use modern multicoated lenses and an efficient shade system. I have lab meters that can measure that kind of thing far more accurately in a controlled environment than any ordinary light meter. I've made HUNDREDS of tests, Pere, densitometer read and often plotted too; and I'm referring to actual sheet film tests, not just roll film. Most of these were done using an expensive thermoregulator that kept dev temp inside 0.1 deg F. I had a good reason to plot film with this level of accuracy due to using films like FP4 and TMX in relation to predictable advanced color printing applications (masks, separation negs etc). This would have been ridiculous overkill for general black and white photography. And your contention that -3.3 consistently lands 0.10 above fbf is nonsense. There's no point trying to explain this to you anymore because you simply aren't grasping the basic issue. FILMS DIFFER IN TOE PERSONALITY. Therefore, no "one shoe fits all" ASA convention is anything more than that - a nominal marketing label that is, at best, only a starting point for personal testing. It doesn't really tell you how those lower values are going to reproduce. Only the actual curve will, relative to your specific exposure and development regimen. What you are doing, Pere, is preaching a religion that requires blind faith in some rote formula you can simply plug into a computer program, and Voila, exposure is solved. The real world of film and light does not work like that. Films differ.

[Pere Casals]

And your contention that -3.3 consistently lands 0.10 above fbf is nonsense. There's no sense trying to explain this anymore because simply aren't getting the basic issue. FILMS DIFFER IN TOE PERSONALITY.

Drew, please read https://en.wikipedia.org/wiki/Film_speed Determining film speed chapter and please tell me how it is possible that a -3.3 exposure is not aiming 0.1D (over F+B), without mattering the kind of toe we have.

With any kind of toe film speed is calculated to give the same 0.1 at -3.3 with normal development, toe personality does not matter for that, at all.

[Drew Wiley]

The storm is clearing and I'm about to go out and shoot, Pere. I wish you well and recognize that numerous people like things like apps for simplifying exposure issues, and that to some degree your formula will probably work, but only in a generic sense. There's no point discussing this further unless you are willing to study it in more depth than you already have. There are all kinds of relevant factor you seem unaware of.

[Pere Casals]

The storm is clearing and I'm about to go out and shoot, Pere. I wish you well and recognize that numerous people like things like apps for simplifying exposure issues, and that to some degree your formula will probably work, but only in a generic sense. There's no point discussing this further unless you are willing to study it in more depth than you already have. There are all kinds of relevant factor you seem unaware of.

Drew, ISO speed is calculated from this graph:

https://upload.wikimedia.org/wikipedia/commons/thumb/c/ca/ISO6speedMethod.png/540px-ISO6speedMethod.png

When we have the "m" exposure, in lux·second, we multiply that by 10, and that value is aimed by meters if using the rated ISO speed, with 1/6 stop margin depending on meter manufacturer.

You may now that 3.3 stops is x10...

So, Drew, where is the toe personality in the calculation?. -3.3 is 0.1D over BF with Normal. Always. This is factual... Any deviation is from inaccuracies in the manufacturing/metering/exposure/processing.

[Drew Wiley]

I don't mean to be rude, Pere, but I'm done unless you're willing to at least think over what I've already repeatedly stated. Everything that you contend is written in stone, simply isn't. You're in the realm of hypothetical generalities and elementary stereotypes rather than real-world specifics. Not all curves are the same, just as not all films are the same. And effective speed is highly dependent upon the specific character of the toe or bottom of the curve itself. What you just gave was a textbook-style diagram showing a very long toe and conspicuous slow drift up onto the shoulder. Now go look up a family of curves for something like Kodak Super-XX, and for sake of learning, note just how different those are from your textbook curve; or in case of a current film, either version of TMax. The curve you posted is almost like old Plus-X, with a very long toe, the very opposite kind of film in terms of shadow rendering ability.

[Pere Casals]

Everything that you contend is written in stone, simply isn't.

You are right, simply not written in stone: It's written in the ISO 6:1993, harder than in any stone.

[Tin Can]

"This standard was last reviewed and confirmed in 2015. Therefore this version remains current."



You are right, simply not written in stone: It's written in the ISO 2240:2003 , harder than in any stone.

[Pere Casals]

I corrected ISO 2240:2003 by ISO 6:1993 https://www.iso.org/standard/3580.html
(This standard was last reviewed and confirmed in 2018. Therefore this version remains current.)

ISO 2240:2003 is for color slides...

[Tin Can]

Yes, I saw that

I like how you backup your facts with links

[Drew Wiley]

(Still waiting for the storm to clear). To hell with Kindergarten level links, Randy. Please tell me something I haven't already known for the past fifty years! Get a good sensitometry textbook and read it while you're snowed in. It's all about interpreting the curves, not just posting a generic blackboard sample curve from Film 101! That whole speed point convention is for sake of generically pigeonholing film speeds that take off like a commercial airliner at a modest angle of entry (long toe) before they achieve cruising altitude (the straight line section of the curve). It at least gives you something. But some films take off more like an F15. Yet with special developers, I can make even those predictably behave like a hoverboard just above the ground. So the name of the game is APPLIED sensitometry. Otherwise, you're just a film carton labeler. What both of you call "facts" simply betrays your very superficial grasp of the entire subject. I'm not interested in disputing some alleged industry convention; I had to deal with those for decades - but that's all it is, a convenience protocol which might or MIGHT NOT help you make more accurate exposures. Did every single pressure gauge where you once worked, Randy, imply the same thing? - as if every pipe and device to which they were connected was intended to have the same amount of pressure? Do I want the same air pressure cleaning off a delicate negative as I use for a nail gun? Same goes for toe placement on film. It's all relative to the specific application. Box speed ratings don't change the need to think things out first, and no palm app or internal camera chip is a substitute for using one's own brain. Gadzooks.

[Pere Casals]

So the name of the game is APPLIED sensitometry.

Drew, this is applied sensitometry...

This is important because if we are able to agree on what film does with a Normal development and ISO speed then we may debate about what film does in non standard conditions. If not we are enterely lost and then we have no way to communicate and share our experiences with advanced processings.

187108

[Bill Burk]

Drew wants you to look in the region of the characteristic curve to the left of m

If you've got the rattler's head a knuckle above the ground, he can stick his tongue straight down or across to the left. This can mean the two films have different real speeds. It's not much, just as far as the snake can spit his tongue, but Drew wants you to recognize there is potential for two films to have the same ASA speed and at the same time have two different "True film speeds".

My thought is that ASA speed's not a measure of a film's true speed. It's a standard that defines what a manufacturer can claim. It does give a basis for comparison, for that I am grateful.

I also think you will find frustration trying to get 0.1 density on your film. My shadows tend towards 0.25 to 0.4 because of flare. I could “feed back” the higher than necessary densities and choose to increase my EI, but I like the longer printing times

[Drew Wiley]

Well, right down there in the rattler's den is where shadow gradation begins with certain films, at least in the kinds of mtn and desert conditions I often encounter. But let me try a little different approach with Pere and Randy : What specific step tablet do each of your use for your own densitometer plots? For purposes of future discussion it will help to know if it's on a clear or yellowish base. But for the present, please note that in either case, some kind of commercially available film was involved, yet there's not only an extremely long 21-step range, but that each of these steps are evenly spaced over the entire range, indicating the whole thing, almost right down to the fbf, was exposed onto the straight line section of the film curve. Now using whatever exposure model you wish, and any film you think is appropriate, try to contact print a replica of that step tablet with exactly the same density and step distribution. Once you've figured that out, then do the same thing using each of typically preferred black and white contrast filters. Remember, all these curves have to precisely match (no post-exp PS tweaking); and in this case, there shouldn't be an evident "curve" at all except maybe at the very bottom. But what you'll soon discover, if you don't suffer an outright TKO during the first round, is that not only does the overall gamma shift with significantly different colored filters, but the curve shape itself, and hence your hypothetical speed point. This is a completely different issue than mere filter factors. Then this gets exaggerated as reciprocity failure comes into play. For this reason I suspect your "True Film Speed" model of exposure, seemingly brought into discussion for sake of simplifying exposure and development issues in large format photography, is actually less predictable than ordinary ole Zone System lingo, which at least allows one to add discrete steps below the generic Zone 2 boundary if necessary. Your model might work fine for moderate exposure scenes, but sure as heck not when your hand is right next to that rattler's hole. ... The other day I was at the camera store and they have access to every bells n' whistles current Nikon, Canon, and Fuji camera you can think of, plus a lot of automated used film cameras. But even though they sell TMax film too, not one of them working there has had any luck predictably using TMax themselves. That's because they're all addicted to fancy TTL algorithms and don't know how to use a basic light meter. Those chipped algorithms might be great for sports or other sudden action photography, but they were never meant to peek down the snake burrow where a lot of the action begins in terms of full rich print gradation.

[interneg]

My thought is that ASA speed's not a measure of a film's true speed. It's a standard that defines what a manufacturer can claim. It does give a basis for comparison, for that I am grateful.


And that's about all the ISO rating is meant to be - the rest is about learning to use the film within a specific process - namely how its curve behaviour affects what you want it to do relative to the paper & light source you are printing with. And theory won't get anyone as far as expending a few dozen sheets of film & some paper - technically speaking, making a 'good' LF neg & print is really pretty easy at moderate sizes - the refinements can come later. Densitometers are very good for process control & for getting a handle on film/ paper curve behaviour if needed - other than that, I'm increasingly of the view that people use them as a technological excuse for a lack of interpretive printing ability and/ or a device to hide a lack of real world printing experience behind.

[Pere Casals]

Bill, I don't say if we have to use 0.1D for our shadows or not...

What I say is that "m" point is our main reference point because it's the calibrated point from what "true speed" is stablished with Normal development. And we also know that under speed point exposure we have onlya 0.1D range for all remaing toe length at left of "m".

And of course the "m" may shift with a non standard development....

Fuji, Kodak, and Ilford say the true ISO speeds in the datasheets for BW, color and slides. Foma 200/400 datasheets are for fun...

We don't need understand what are ISO speed and speed point for a normal developement... Personal speeds also work !

But also what ISO 6:1993 says it's extremly clear: 0.1D+B+F at -3.3, under normal gradient with the specified developer. This is not an opinion, but an industrial norm.

[Drew Wiley]

You apparently posted at the same time as me, Interneg, and I agree with you, at least as far as conventional black and white printing is involved. My own technical tangle with densitometry was a necessary aspect of making color prints that averaged around a hundred US dollars a pop in materials. At that rate, full predictability of various accessory black and white mask densities and curves - or rather, families of curves, was a must, not an option. Making matched color separation negatives is even more demanding and necessarily takes into account the full film scale, and not just that lesser portion suitable for ordinary black and white printing. Even different batches of the same film might need to be tested and plotted. But so far, TMax sheet film quality control has been excellent and highly predictable. But some EU films have not only had quality issues, but ISO rating that seem to be nonsensically overoptimistic. Even Ilford films, though very consistent per quality in my experience, interpolate the toe too much and are rated too high an ISO for real world expectations. So as far as I'm concerned, in terms of overall manufacturer to manufacturer usage, all this "true film speed talk" completely fails to take into account one of the most significant variables of all : the "Marketing BS Coefficient".

[Pere Casals]

What specific step tablet do each of your use for your own densitometer plots?

Stouffer T2115, DIY calibrated with my NUCLEAR ASSOCIATES Model 07-443 densitometer, that came with a calibrated wedge.

You can see it here: https://www.flickr.com/photos/125592977@N05/33551104771/in/dateposted-public/



But so far, TMax sheet film quality control has been excellent and highly predictable. ....Ilford films

Ilford film are also well rated in ISO speed, but Kodak films has less speed change with aging.

Kodak and Fuji shows real Lux·seconds in the datasheets' graphs ...so in that case there is no doubt about the exposure/density in the meter point and in the speed point. They fullfill ISO 6:1993.

[Drew Wiley]

OK. That's a good start. Now can you surmise, by its visible and measurable characteristics, exactly what kind of film that step tablet was probably made on? It's not a trick question, but relevant to an appraisal of your whole model of thought. Of course, their master tablet used to make their film version was probably tweaked a tiny bit, but not enough to alter the discussion.

[Pere Casals]

exactly what kind of film that step tablet was probably made on?

This is absolutely irrelevant, what matters is this: http://www.stouffer.net/T2115spec.htm

https://web.archive.org/web/20170719184944/http://www.stouffer.net/T2115spec.htm

[interneg]

Drew - I intended colour separations as implicit in 'process controls' - and Foma's datasheets are pretty honest about the effective film speed at specific gamma. The Ilford/ Kodak differences are more complex & I suspect have as much to do with their preference for slightly different analytical choices - G-bar Vs CI etc, and further material design choices/ relationships (ie, more or less solvent developers' effects on specific grain structures relative to iodide content/ placement). And I have many, many, many better things to do than carry out a rigorous comparison (which would be pointless anyway unless I had a microdensitometer).

[Pere Casals]

unless I had a microdensitometer).

I have one:

187113

It checks density of a single pixel with 16 bits accuracy. It takes advantage from scanner precision. If you want you may try it...

[Drew Wiley]

Hi Interneg - Foma 200 is essentially worthless for actual color separation work. More marketing hype just to make it appear equivalent to Super-XX applications. Not only is the quality control infamously dicey, but this particular film is incapable of the gamma boost necessary. All the "straight line" 200's (Kodak Super -XX and Color Sep Film, Bergger 200, and now Foma/Arista/Classic 200) have trouble with blue separation gamma to begin with. But the idea was to get it as high as possible to allow something in a subsequent step (like dev of dye transfer matrices themselves) to make up the balance. Ilford's FP4 can also alternately be used for separations, but not anywhere near as far into the toe; and it also suffers the blue issue. Of course, nowadays curve can be PS tweaked if scanning is part of the overall protocol; but even then, it helps to be close right out of the gate. Then there's the headache of having to develop each of the 3 or possibly 4 different separation differently. TMax 100 was engineered very intelligently, and is the only film I'm aware of which can be batch developed for all 3 separation together with complete consistency, provided one discovers the sweet spot in exposure itself (which does take a fair amount of work whether in-camera in the field, or via lab RGB internegs. But this feature of TMX has apparently been long forgotten, since all-film workflow is apparently limited to a few remaining dinosaurs like me. I find it fun. But if you've figured out how to tame Foma 200 (non-digitally), I'd sure like to hear about it. I gave up on it even for general shooting due to all the zits and linear scratches or cracks on the emulsion.

[Drew Wiley]

Pere, no need to think in terms of microtonality. We're not trying to measure edge effect here, but the density of each step on the tablet, which has a decently large area. From what you just posted, the chart accompanying your step tablet does not factor in the fbf because it's minimal. But since it's apparently .05, and each step is close to the intended .15 increment, only the very first step falls a bit short of that amount at 0.1 density gain. I'm not an industrial spy, but do have a pretty good idea of not only the specific film involved but the developer and its concentration. Don't want to give that away just yet. And please keep in mind I'm not trying to invalidate your exposure model, but am trying to point out how the real-world utility of any model first requires acknowledgement of its inherent limitations. None are perfect. In this instance you've got a step tablet, an actual piece of film, that defies some of your hypothetical methodology based upon speed point. Since speed point is, as you say, minus 3.3, what is it minus 3.3 from what? Presumably middle 18% gray. Where, for example, would you place Zone V relative to patches on this step tablet itself, which does not settle into a gentle extrapolated curve at all, but a very steep one, almost completely linear.

[interneg]

Hi Interneg - Foma 200 is essentially worthless for actual color separation work.

Would not disagree - my comments were unclear, & were meant to refer only to Foma's relative effective speed compared to the box, not suitability for making seps!

Regarding TMX, I've seen an old official Kodak document recommending it specifically for making in-camera dye transfer seps for essentially the reasons you outline (and TMZ too, perhaps bizarrely - were people afraid that Super-XX was insufficiently grainy!?)

All this is doing is reminding me I need to get on with seeing if frosted mylar/ duralar can be used as means of generating an analogue stochastic screen for processes other than offset printing...

[interneg]

I have one:

187113

It checks density of a single pixel with 16 bits accuracy. It takes advantage from scanner precision. If you want you may try it...

Without going way off-topic, it'd need a variety of apertures down to 1 micron & potentially an x-ray source to be competitive with what manufacturers have in their R&D labs.

[Pere Casals]

But since it's apparently .05, and each step is close to the intended .15 increment, only the very first step falls a bit short of that amount at 0.1 density gain. , the chart accompanying your step tablet does not factor in the fbf

As the reference you can place any kind of step tablet, of course it interpolates from densities in the step tablet, you load the true calibration of the step tablet. Works perfect...

Of course it factors the fbf, that screen shot is of the desnsitometer tab, there is another tab for film calibration...




And please keep in mind I'm not trying to invalidate your exposure model,

It's not my exposure model, it's the ISO calibration model that uses as reference the speed point and the standard contrast.




Since speed point is, as you say, minus 3.3, what is it minus 3.3 from?

minus 3.3 from the meter point with the rated ISO speed setting, this is a particular Lux·second exposure on film that is very well determinated.

From the EV100 table and from ISO speed you have the lux·second on film that builds 0.72D and 0.1D with standard development, so you also have the light power needed on a 18% grey card to build each of these densities throught the lens. If metering is not done TTL then one has to guess/measure the lens transmission, F/ vs T/ factor.

[Drew Wiley]

TMZ would have been a bad choice. Kodak was not entirely objective when it threw out certain product suggestions. I know the specific persons who wrote some of those publications, who never in fact tested certain hypothetical applications. In dye transfer work the dyes bleed a bit anyway, so the grain pattern is not generally visible unless the print was made via enlarged negs from something tiny like 35mm film. Sharpness is not the strong point of that particular process. But there are ways to minimize bleeding. But the big commercial houses used a separation-of-tasks bulk workflow, much like an assembly line, and couldn't slow things down by the extra steps needed to optimize sharpness. My own separations on modern films should allow a significant improvement in this respect, especially if used alternately to print RA4 chromogenic papers in registered sequential RGB mode, which I'm equipped to do. But the hitch is that, ideally, DT separations include the net effect of prior mask-correcting for dye bias, which means they won't be ideal for the somewhat differing characteristics of chromogenic dye curves. I'm not quite at that point. Last round I did RA4 prints via 8x10 corrected contact internegatives from color chromes, and most of the results were quite encouraging. A lot better he control than printing directly from color neg film originals, and more acceptable he repro for me than inkjet for sure.

[Pere Casals]

Without going way off-topic, it'd need a variety of apertures down to 1 micron & potentially an x-ray source to be competitive with what manufacturers have in their R&D labs.

Well, this densitometer is 2000dpi able with a cheap flatbed, but if you use a x5 you would obtain until 6900dpi, so around 3.6 micrometers, not bad, but far from 1 micron with rx RX.

Many microdensitometers are used beyond 10 micrometers. Hmmm perhaps it would do it !!!

[Bill Burk]

187108

Speed Point to METER should be 1 log unit, your drawings always seem a little wider.
And if you are going to use 2 decimal precision for 0.62, why not change your 3.3 notation to 3.33 stops to more clearly illustrate that it's 3 and a third.

Now I don't believe ASA standard actually includes the definition of 1.0 Log H Speed Point to METER. I think it's a "fact". I mean, it's right (or at least within 1/6 stop of being right), but I think that I would find that in meter calibration standards. And it's something that works well working backwards to confirm 0.1 in camera tests when you reduce the exposure to attempt a gray exposure at that point.

But to test, say by setting your Nikon to 4000 for a 400 speed film and shooting something flat and gray... that will get you 0.1 density.

But when you set the meter back to 400 and shoot a regular picture. Some part of the scene which you might prove has 1/10th the luminance, will not have 0.1 density on your negative because some other brighter part of the picture contributes some "light pollution" inside the camera body. It's like being in the city, you can't always see all the stars. That's where flare raises your shadows up.

[Bill Burk]

A little more backstory as it’s been taught to me.

It was DIN in Europe who wanted the speed point to be 0.1

In the US, Kodak wanted it to be where the curve slope was 0.3 times the average gradient.

To settle the matter, a compromise was decided to make the speed point 0.1 but add the contrast requirements.

The idea was to allow everyone to save face and “be right”.

The 0.3 gradient typically falls 0.29 to the left of m when the contrast parameters are met. That was included in the speed definition.

That 0.3 gradient is really the point under consideration as the last point where you want any part of your picture to land

From there, a standard image has 7 2/3 stop subject luminance range, less 0.4 flare, plus safety factor. You also figure in that the average reflectance of an average metered scene might be 12%, which is considered in the speed definition (but I don’t know where it is revealed)

[Bill Burk]

Here's a drawing I made on an arbitrary real film characteristic curve.

I illustrated the "true speed point" and the ASA points as well as where the standard picture should fall and how it fits the negative.

Since the APX100 was very old, I lost some speed. So I illustrated meter points of 100 80 and 64 since the useful film speed is one of those.


http://www.beefalobill.com/images/2019-01-31-0002.pdf

[Pere Casals]

Speed Point to METER should be 1 log unit, your drawings always seem a little wider.

You are right, this was made fast with MS Paint to tell how graphs in datasheets can be read.


And if you are going to use 2 decimal precision for 0.62, why not change your 3.3 notation to 3.33 stops to more clearly illustrate that it's 3 and a third.

No problem in using 3.33...

Anyway 0.62 and 3.3 is same precision in the calculations, 2 significant figures, in scientific notation 6.2E-1 and 3.3E0.



Now I don't believe ASA standard actually includes the definition of 1.0 Log H Speed Point to METER.

Bill, 1.0H this is exact from the formula, the x10 amount of lux.seconds is related to speed with the 800 constant (or 0.8, lux or millilux ) see:

https://www.kodak.com/uploadedfiles/motion/US_plugins_acrobat_en_motion_education_sensitometry_workbook.pdf.
https://web.archive.org/web/20180731074413/https://www.kodak.com/uploadedfiles/motion/US_plugins_acrobat_en_motion_education_sensitometry_workbook.pdf

Pre 1960 it was 1.3H (20x, 4.3 stops), in 1960 the 1.3H was moved to 1.0H (10x 3.3 stops) for the speed calculation to just double the box speed without manufacturing changes. But 1.3H remained post 1960 for the gradient determination... 1.3 is what we still see in the speed detemination graphs !! but the constant in the formula moved from 400 to 800 in 1960....

Because of that now (since 1960) the meter point is not at 1.3H from "m" as we see it in the ISO triangle, but 0.3H at left of it...




I mean, it's right (or at least within 1/6 stop of being right), but I think that I would find that in meter calibration standards.

The 1/6 stop margin in meters this not about sensitometry, sensitometry takes direct lux.second on film and what happens in the other side of the lens is abstract.

Exposure meters have no tight norm, manufacturers may vary two constats to aim the precise ISO lux·second on film, but as there is a debate in the standard grey reflectance, spectral sensitivity and etc we have 1/6 flavours.




But to test, say by setting your Nikon to 4000 for a 400 speed film and shooting something flat and gray... that will get you 0.1 density.

This is what all of us should test at least once in a lifetime, just to be aware of our reference points, and to know if a manufacturer is missleading customers.

[Drew Wiley]

Pere - the quality control of most gray cards as well as reflection step tablets was simply awful. They varied not only in density but actual color from brand to brand, and even within the same brand, etc. They fade too. I measured a whole stack of them once on a high-quality spectrophotometer, and all were off, some way off. You have to go to something manufactured under tight control by a specialty company, like a MacBeath Color Checker chart and its gray scale, and then keep it safe from dirt of fading. As far as meters go, all my Pentax and Minolta digital spot meters read exactly the same over the full range. If there is even a third of a stop of deviance anywhere, I have it recalibrated by the same outfit that does this for Hollywood film makers. Ordinary meters are not sensitive enough for serious lab work; but they are plenty good for general field and studio usage. And I personally do expect more critical performance in the shadows of scenes than what any of these various voodoo INTERPOLATED tweaks of "official" ISO speed ratings pretend to predict.

[Alan Klein]

What's with the difference between reading reflective off a gray card and incident readings using the same meter?

[Bill Burk]

Bill, 1.0H this is exact from the formula, the x10 amount of lux.seconds is related to speed with the 800 constant (or 0.8, lux or millilux ) see:

https://www.kodak.com/uploadedfiles/motion/US_plugins_acrobat_en_motion_education_sensitometry_workbook.pdf.
https://web.archive.org/web/20180731074413/https://www.kodak.com/uploadedfiles/motion/US_plugins_acrobat_en_motion_education_sensitometry_workbook.pdf

Pre 1960 it was 1.3H (20x, 4.3 stops), in 1960 the 1.3H was moved to 1.0H (10x 3.3 stops) for the speed calculation to just double the box speed without manufacturing changes. But 1.3H remained post 1960 for the gradient determination... 1.3 is what we still see in the speed detemination graphs !! but the constant in the formula moved from 400 to 800 in 1960....

Because of that now (since 1960) the meter point is not at 1.3H from "m" as we see it in the ISO triangle, but 0.3H at left of it...


I don't see 1.0H (3.3 stops or 10x) in the workbook you linked.

As far as I know, I was the one who claimed that. And I confirmed it with this test.

http://beefalobill.com/imgs/tmxaim.jpg

Check your notes and make sure you didn't base your benchmark on something I said.

When I say "within 1/6 stop", I'm not talking about the variations allowed. I'm talking about my test result which is off 1/6 stop from proving 1.0 log H from speed point to meter point.

I've convinced myself that my test was off 1/6 stop because of normal test variation.

Rounding is important to me because the amount and direction my test was off is the same amount and direction that you get by rounding 3.33 stops to 3.3 stops.

It's not meaningless to me, it's a "remarkable" difference. By remarkable, I don't mean amazing, I just mean it's enough to make a remark about.

[Pere Casals]

I don't see 1.0H (3.3 stops or 10x) in the workbook you linked.

Yes, you are right... only 1.3H is referenced in the gradient calculation. And 1.3H was the pre 1960 interval that was reduced by 1 Stop.

But it is clear that 1.0H is what gives 0.62D over "m" density, with the Normal development. This is the key concept.

0.62D over m, or 0.72D over Fog+Base is the standard density in a BW negative aimed by the ISO process, so by the industry. This included manufacturers of film(box speed), slr cameras/meters(calibration), processing equipment and labs(ISO normal processing).

My guess is that the ISO Norm that enlights the more is ISO 2721:1982 for internal (TTL) meters, still applicable to film cameras but not to digital cameras (that have ISO 2721:2013).

The ISO 2721:1982 document has to be payed, but here it is quoted mentioning the x10 factor, so 1.0H,

please see here page 4:

http://dougkerr.net/Pumpkin/articles/Exposure_calibration.pdf
https://web.archive.org/web/20170213005754/http://dougkerr.net/Pumpkin/articles/Exposure_calibration.pdf

The standard for internal meters it has less "complications" because it's a direct reading of the light that is to reach the film, without having to guess the lens transmssion or the good reflectance value.

Well, this is at least what I concluded, being the internal meter calibration norm what is the most meaningful to me, as external meters have many practical difficulties to be better standarized (two floating constants!).

[m00dawg]

No!!!!

http://www.stouffer.net/T2115spec.htm T2115, $7

Or the calibrated one $17, T2115C http://www.stouffer.net/Productlist.htm


You scan your negative alongside with the Stouffer and by comparing you have a densitometer !!! :)

Also soon I'll release this freeware: https://www.largeformatphotography.info/forum/showthread.php?150045-New-darkroom-calibration-software to make it easier.

You make the contact copies of the stouffer, you scan the stouffer and the copies, et voilà... you have the curves with a click. Just buy a $15 densitometer if you want absolute units for light, like in the kodak datasheets.

Started reading BTZS last week (was good reading material for some flights I had to take) and yeah, after reading multiple chapters on making graphs by hand...I'm really looking forward to your tool! Book itself was heavier reading than I thought. Really gets deep with a topical introduction on why. I didn't think I'd be quite so hands on so soon so I topically read the parts about how to make graphs (I'll have to re-read those I'm sure).

Does make me excited to get a step tablet and do some tests of paper and films though. It explained that reasonably well.

[Drew Wiley]

Pere, here's the problem I have with the Speed Point conventions, regardless of which specific version of it is used. They all INTERPOLATE the bottom of the curve; and that is exactly where I want to know what is REALLY going on. In other words, I don't want interpolated data between two artificial points, but recognition of the actual curve characteristics down there. For example, on a 21 step tablet itself, shadow gradation instantly climbs in a predictable ratio almost from the very bottom of the curve. This tells you that there are in fact films capable of a straight line almost right out of the gate from fbf, and that they behave quite differently in that respect from many other films - the very thinnest step above fbf is capable of showing distinct shadow gradation in the print (although one might be wise to give themselves a little more margin of safety when metering things in the field). If you take that very same speed point and apply to something like HP5, however, it will take more steps to achieve the same straight line section of the curve. So my point is not to argue about the specific industrial formulas about ISO, as if they're even consistently followed brand to brand - but to question the suitablilty of any "speed point" model of exposure if one needs extra shadow differentiation than generic dumbed-down rote exposure models allow. Half the secret in choosing an appropriate film seems to be in recognizing the specific rather than artificially pigeonholed characteristics of the toe. It's how I routinely work.

[Pere Casals]

Pere, here's the problem I have with the Speed Point conventions, regardless of which specific version of it is used. They all INTERPOLATE the bottom of the curve;

As you say the curve may not be completely linear, to me this is about -/+ 1/3 stops for deep shadow detail, usually less...

...while processing/metering/exposing/goût may move 1.5 to 2 stops the personal speed from ISO speed.

[Pere Casals]

Started reading BTZS last week (was good reading material for some flights I had to take) and yeah, after reading multiple chapters on making graphs by hand...I'm really looking forward to your tool! Book itself was heavier reading than I thought. Really gets deep with a topical introduction on why. I didn't think I'd be quite so hands on so soon so I topically read the parts about how to make graphs (I'll have to re-read those I'm sure). Does make me excited to get a step tablet and do some tests of paper and films though. It explained that reasonably well.

First, let me point that by no means sensitometry or exposure systems are the most important ingredient in a great photograph. IMHO this is about spritual connection between photographer and subject, just a personal opinion.

But also let me recommend again you to make the necessary effort to understand BTZS in depth. A key concept is logarithmic scale, not nice having to deal with Logs, but's necessary. Logs are used because logarithmic scale is related to the human vision scale, so the way we perceive light. So we have to get practice in that.

By understanding and having some practice in BTZS you gain in self-confidence, you know what film does with light. You will be aware if without thinking much you can get your shot or if you need to meter/process/calibrate with accuracy to get the image you want.


By the way, let me show who wrote BTZS (Left):

187269

[m00dawg]

First, let me point that by no means sensitometry or exposure systems are the most important ingredient in a great photograph. IMHO this is about spritual connection between photographer and subject, just a personal opinion.

But also let me recommend again you to make the necessary effort to understand BTZS in depth. A key concept is logarithmic scale, not nice having to deal with Logs, but's necessary. Logs are used because logarithmic scale is related to the human vision scale, so the way we perceive light. So we have to get practice in that.

Oh yes I don't disagree, though I did get a bit lost. There's a lot of time taken to work on graphs by hand which is both neat and useful, but there were some assumptions made I've had to do that - I haven't in decades and am more used to digital domain tools (GNU graph, a spreadsheet, etc.). I can see some benefits in pencil and paper here since some of the exercise involves doing things I don't normally do on a computer (a few I don't know how to precisely).

The paper tests seemed decently clear and I can see their use pretty quick - e.g. exposing using a geometric series makes quite a lot of sense and testing paper grades is something I now know how to do (still need to get a tablet). Testing filters is something I'm excited to try - I can both see if my ND filters shift things (if they don't transmit green and blue equally for instance) and can determine how well my new V54 cold light responds to paper grades. Highly useful.

Actually exposing the film as well made sense although I don't think I have the tools to do it properly. I do have a few (mechanical) LF lenses I could perhaps figure out how to mount to my enlarger. I was going to say I was worried the mechanical lens wouldn’t be accurate, but as long as it's accurate for the same 5 test exposures it should be ok? (e.g. if 1/2" speed is more like 575ms instead of 500ms).

Once I have those though, the conclusions drawn from it when you start looking at ISO and development start to get hazy and I got totally lost when having to map the zone system on-top when looking at expansion/contraction. Makes me wonder if there is a local informal class I can take (we have an art college here) so it's more hands on. I have had some AHA! moments but mostly with the paper and geometric sequences.

I suspect I'm getting stuck on the "B" part of BTZS because I should probably get a handle on what AA described in The Negative first.

Anyways haha yeah that's a funny picture. I like Davis' face there, gave me a chuckle!

[cowanw]

By the way, let me show who wrote BTZS (Left):

187269


Credit to Oren Grad and acknowledgement to Mike Johnston.

[Pere Casals]

Yes...
https://theonlinephotographer.typepad.com/the_online_photographer/2008/06/freaky-monday.html
https://web.archive.org/web/20121115034119/https://theonlinephotographer.typepad.com/the_online_photographer/2008/06/freaky-monday.html

[Bill Burk]

Actually exposing the film as well made sense although I don't think I have the tools to do it properly. I do have a few (mechanical) LF lenses I could perhaps figure out how to mount to my enlarger. I was going to say I was worried the mechanical lens wouldn’t be accurate, but as long as it's accurate for the same 5 test exposures it should be ok? (e.g. if 1/2" speed is more like 575ms instead of 500ms).

Once I have those though, the conclusions drawn from it when you start looking at ISO and development start to get hazy and I got totally lost when having to map the zone system on-top when looking at expansion/contraction. Makes me wonder if there is a local informal class I can take (we have an art college here) so it's more hands on. I have had some AHA! moments but mostly with the paper and geometric sequences.

I suspect I'm getting stuck on the "B" part of BTZS because I should probably get a handle on what AA described in The Negative first.

Maybe I could sell you a copy of my booklet (free):

http://beefalobill.com/imgs/20150812%20CallingYourShot-DividedAttention.pdf

Do you have any old "electronic" SLR cameras in your arsenal? For example a Minolta X370 would give you a good (quartz-controlled) 1/2 second time.

Consistency is the name of the game here. Not so sure the V54 can give that to you though. Do you have another enlarger, maybe one that takes regular light bulbs?

The B of BTZS is for "Beyond" and means "using an incident meter". The nice thing about BTZS is that it covers the Zone System pretty well... then takes you Beyond.

You can treat them as different chapters and grapple with them one at a time.

[Bill Burk]

My guess is that the ISO Norm that enlights the more is ISO 2721:1982 for internal (TTL) meters, still applicable to film cameras but not to digital cameras (that have ISO 2721:2013).

The ISO 2721:1982 document has to be payed, but here it is quoted mentioning the x10 factor, so 1.0H,

please see here page 4:

http://dougkerr.net/Pumpkin/articles/Exposure_calibration.pdf
https://web.archive.org/web/20170213005754/http://dougkerr.net/Pumpkin/articles/Exposure_calibration.pdf

The standard for internal meters it has less "complications" because it's a direct reading of the light that is to reach the film, without having to guess the lens transmssion or the good reflectance value.

Ah, yes... The 1.0H would be in a standard for the meter (or camera) calibration.

Now if you remember my story where I didn't perfectly confirm 1.0H but found slightly less, the fact my OM-4 missed by about 0.03 makes me think a couple things could be at play. The OM-4 has off the film metering so it could give exactly the right amount of exposure if it wanted to. But maybe its calibration was reduced 0.03 to match "everything else", Olympus wanted people to get the same results whether they used the auto exposure or they used one of their trusted light meters.

For example, the best light meter calibration might place the meter point at 1.0H from the speed point but due to transmission loss, in a camera the light hitting film falls about 0.03 less.

So Olympus made the automatic exposure hit 0.03 less to match.

So maybe 1.0H is the meter calibration constant, but the film is expected to receive 0.97H

[Pere Casals]

For example, the best light meter calibration might place the meter point at 1.0H from the speed point but due to transmission loss, in a camera the light hitting film falls about 0.03 less.

Bill, perhaps that 0.03H shift may also be of spectral nature, just another possibility.

A perfect BW meter should match the same spectral sensitivity than in the particular film we are using...

But in practice we have a chain of spectral transformations. First there is the light source spectrum, then we have the subject's spectral reflectance (a gray subject may not have a flat response, but a balanced response)...

Then the Zuiko lens (praised because of his colors) also it may transform a bit the spectrum, and finally we may have some different spectral sensitivity in each meter sensor.

Anyway a 0.03H shift is not much in practice...

My view is that we always may need some safety factor for the deep shadows we want to record. If our metering/exposure is very accurate then this safety factor is way narrower...

...for example if we have no shutter tester for our LF shutters then our good safety factor may grow remarkably...

This may be irrelevant for many shots, but IMHO some shots may require that we squezze all the film capability. And Velvia always wants precision !

[interneg]

http://beefalobill.com/imgs/20150812%20CallingYourShot-DividedAttention.pdf

...

The B of BTZS is for "Beyond" and means "using an incident meter".


The Kodak tables you quote in your pdf (and an idea of time/ CI curves - manufacturers data is not the worst starting point) + flare correction (as you discuss) + an incident meter or spot meter are about all that is needed to really get a handle on exposure & development... That people want to make it so wilfully difficult and obscurantist never ceases to amaze me. I think a lot of it has to do with a poor analytical & artistic understanding of the visual (as opposed to sensitometric) behaviour of the materials - which is often solved by making more negatives & printing them...

[Pere Casals]

I think a lot of it has to do with a poor analytical & artistic understanding of the visual (as opposed to sensitometric) behaviour of the materials - which is often solved by making more negatives & printing them...

interneg, you are right in that. I don't think that Sally Mann has calibrated the sensitometric curves of the wet plates, while she is exhibiting right now one of the most powerful works in decades. Perhaps she calibrated his process, I've no idea, but I'm pretty sure that his work does not depend on that.

Anyway sensitometry is an straight way to learn how the medium works, to nail exposures, to learn the effects of manipulating the process, and also it's a precise tool that's extremly useful in some situations.

IMHO it's more important learning what BTZS says than using calibrations. There is a lot of gossip around about films and processing. Having the BTZS knowledge one may discriminate what is worth and what is gossip.

...but I agree, one has to hit the boulder with a hammer to make a Pietà, in the darkroom this is having hands wet, and growing in determinaton after every pitfall. I'm a rookie printer, but I learned that the first day.

"Previsualization is where the Zone System really shines" (http://beefalobill.com/imgs/20150812%20CallingYourShot-DividedAttention.pdf)

[m00dawg]

I'm still trying to work out the relationship between film testing with the BTZS methods and how the film looks (e.g. films which are more contrasty vs less - so far book hasn't addressed that much). Be that as it may, even now I think doing tests will prove useful since, at the very least, it may help validate my own personal ISO and developing times to start and I can start filling in the gaps late.

That second issue (developing times) has me stumped though. The book suggests, and rightly so, to use BTZS tubes. I prefer to use a JOBO rotary tank (with a motorized rotary I built myself) with XTOL (Replenished) as my standard setup. Concern I have with the tubes is that it's not going to be a good way to evaluate development times accurately between it and my preferred solution because of agitation differences, etc. (right?). So the only way I can really determine dev times is doing a full development cycle with the methods I do use. Tedious at best and adds in some wiggle room when using replenishment that could skew fully accurate results.

Am I super off base in thinking that, or will using BTZS tubes theoretically get me close enough to extrapolate to a rotary? It's an expensive gamble to just buy the tubes and try it which is why I'm asking.

[Pere Casals]

how the film looks (e.g. films which are more contrasty vs less - so far book hasn't addressed that much).

With normal development all films have same (or similar) contrast, this is a 0.62D augmentation for each 3.3 stops. I say "similar" because curves may not be exactly straight lines, so we may have slightly different flavours.

What influences the contrast in the negative is development time.



That second issue (developing times) has me stumped though. The book suggests, and rightly so, to use BTZS tubes. I prefer to use a JOBO rotary tank (with a motorized rotary I built myself) with XTOL (Replenished) as my standard setup. Concern I have with the tubes is that it's not going to be a good way to evaluate development times accurately between it and my preferred solution because of agitation differences, etc. (right?). So the only way I can really determine dev times is doing a full development cycle with the methods I do use. Tedious at best and adds in some wiggle room when using replenishment that could skew fully accurate results.

The tubes and the jobo rotary have exactly the same effect, IMHO, so don't worry.

With tray development you may use diluted development and low agitation to provocate chem exhaustion in the highlights, so you prevent a bit blowing the highlights, so you have some compensating effect.

But any contiunous agitation processing (tubes or rotary) will renew well chem inside emulsion before it can be exhausted by intense development(in the highlights), so the tubes and rotary are same.

[m00dawg]

With normal development all films have same (or similar) contrast, this is a 0.62D augmentation for each 3.3 stops. I say "similar" because curves may not be exactly straight lines, so we may have slightly different flavours.

What influences the contrast in the negative is development time.




The tubes and the jobo rotary have exactly the same effect, IMHO, so don't worry.

With tray development you may use diluted development and low agitation to provocate chem exhaustion in the highlights, so you prevent a bit blowing the highlights, so you have some compensating effect.

But any contiunous agitation processing (tubes or rotary) will renew well chem inside emulsion before it can be exhausted by intense development(in the highlights), so the tubes and rotary are same.

That's helpful thank you!!

Actually good point on trays since if I wanted to be both economical with time or money, tray is the only other option but seems like it's more akin to inversion processing? If I'm burning 5 sheets I should perhaps do it right. BTZS I bet will be nice if/when I start to do a lot of -/+ development (I suppose that's part of the point of the system heh!)

Conversation about curves is interesting though - I thought there could be, for instance, short toe and long toe films? This is where I kinda got confused because it implies that any film could look like any other film (speaking about contrast here) if you found the exposure and development settings where they produced close to equivalent curves?

[Pere Casals]

if you found the exposure and development settings where they produced close to equivalent curves?

Please see manufacturer datasheets, they show the curves with different processings, for example you can compare TXP, HP5+, TMY, . Or TMX vs Delta 100 vs and (killed) Neopan.

In general all films are quite linear from -2 to +2. Beyond that interval the toe and the shoulder may have a particular footprint. If you ensure that your shadows are well exposed (say -2) then all films have same situation. Difference are more from grain structure (in small formats, specially) and spectral sensitivity, see also spectral sensitivity curves in the datasheets: Some see more deep red, some have a valley in the 550nm range that separates better skin tones, but filtration has a greater effect....

[m00dawg]

Please see manufacturer datasheets, they show the curves with different processings, for example you can comapare TXP, HP5+, TMY, . Or TMX vs Delta 100 vs and (killed) Neopan.

In general all films are quite linear from -2 to +2. Beyond that interval the toe and the shoulder may have a particular footprint. If you ensure that your shadows are well exposed (say -2) then all films have same situation. Difference are more from grain structure (in small formats, specially) and spectral sensitivity, see also spectral sensitivity curves in the datasheets: Some see more deep red, some have a valley in the 550nm range that separates better skin tones, but filtration ha a greater effect....

Got it, thanks again Pere, that helps!

[Drew Wiley]

Well, you're not quite there yet, Pere, and might need some more time to appreciate all the interesting scenery that potentially lies well below -2. ... So no, m00dawg, there will never be a point at which all films behave the same unless you're talking about zero exposure totally blank film ! Certain films can be made more similar to one another by developer choice and method; but not all films can be, by any means. Be glad they can't. We need different kinds of film personalities.

[Pere Casals]

the interesting scenery that potentially lies well below -2. ...

Well, many times what lies under -2 are problems...

[Drew Wiley]

Yes. And it's up to you whether you want to try to master those basement values or keep a safe distance from them. There's no right or wrong in that particular department, just numerous personal logistical options. Matching your own technique to your own mode of visualization and printing is what counts.

[Pere Casals]

Drew, I fully agree. What is clear is that is we have an accurate metering/exposure the we can go a bit lower.

LF shutters were sold with -/+ 30% accuracy new out the box, so 1/30 could be 1/20 or 1/40 and still in specs.

[Drew Wiley]

Yes, that too. Test your shutter speeds, especially with older lenses. Most modern Copals and Compurs seem to be well within a third of a stop, except at the very highest speeds.

[Bill Burk]

In Todd-Zakia there’s a saying about exposure, “The least, if it is enough, is usually the best.”

I started to think a bit about where exposure is critical. Movies, definitely. So if you are shooting reversal black and white, it will be important to accurately expose each shot in a series “for continuity.” No auto-exposure will do.

When shooting process camera pages of type, the high contrast film may seem forgiving of exposure differences, but the serifs of type can’t tolerate sloppy lighting or exposure. And you can’t really give litho film used like that an ASA rating.

You mentioned Velvia, I checked Galen Rowell’s article about it. He would rate it at 50 for rich color and 40 for more open shadows. So a third stop was significant to him. He would also use ND grads because he figured Velvia could only hold detai 1 1/2 stops above and below the metered point.

I don’t want to have underexposed negatives. I am surely “overcompensating” when I rate TMAX 400 at 250, but it’s what I like now.

I recommend adopting 1.0 log H as the meter calibration point. I’ll keep an eye out for possibility of it being 1/6 stop less, but only if 1.0 continues to prove slightly off.

[Pere Casals]

I started to think a bit about where exposure is critical. Movies, definitely.

I often review scenes shot by Kamiński in The Schindler's List... http://www.peterhogenson.com/blog/2017/7/10/black-and-white-cinematography-schindlers-list.

While still not having skills enough to analyze that impressive work, from it I realized what is mastering a medium. Universal Pictures wanted it in color, Spielberg was allowed to shot it (for free) if also making Jurasic Park. "No Steadicams, no elevated shots, or zoom lenses...", and using Plus-X and Double-X... But this is not simply an impressive work. These are Spielberg and Kamiński, two masters of his tools, sporting divine inspiration.



shooting reversal black and white

This is a personal view. Today film cinematography is scanned and digitally edited, this is a major practical advance, this is how right now Star Wars Episode 9 is crafted. But I find than old cinematography lacking digital edition is simply glorious. My view in that patching with Ps what we did wrong with the medium it's a botched job. Nothing better that capturing light purity.

While I understand the value of image manipulation as a creative tool I also find that authenticity is of high value. To me, this is an strong point of the (BW) slides, photons reflected by subject decided what silver would remain, and we see that.

I found that mastering BW slides is not a joke, here we have to really nail what we do in every step, and calibration job is extremly helpful.




You mentioned Velvia, I checked Galen Rowell’s article about it. He would rate it at 50 for rich color and 40 for more open shadows. So a third stop was significant to him.

Perhaps the 50 vs 40 is related to Center Weighted exposure, a way to speak. While Rowell was using Nikons in the Velvia era that also had spot meter and matrix, he also did a lot before with cameras having only CW, I guess that 40 vs 50 is related to CW metering, so a basic technique in the mountain would be asking uniformity from graded ND and then using CW metering.

Velvia shots have to be nailed, and even with graded filters we should make decissions about priorizing shadows or highlights, of course.



I recommend adopting 1.0 log H as the meter calibration point. I’ll keep an eye out for possibility of it being 1/6 stop less, but only if 1.0 continues to prove slightly off.

I agree. In fact 1.0H it is the ISO internal meter calibration point, a bit problem is practical implemetation of metering. Meters have an spectral response, film has another one, and our subjects are often coloured. So beyond our personal inaccuracies we have an uncertain behaviour from meter depending on the situation, so IMHO we always need some safety factor that exceeds that 1/6...

but in practice, of course, with accurate metering/exposure we nail what we want...

[Drew Wiley]

Bill - you've probably seen Galen's pictures only in books - relatively tiny images. If you have been standing right there, like I have, when more than one lab owner was complaining about NOTHING being in the shadows in his printed enlargements, you'd understand just how poorly Galen understood the technical aspects of photography, as well as why Velvia was a horrible choice for his style of shooting. Then he got into that whole grad filter attempt to put lipstick on a pig, meaning the manner he did it habitually looked blatantly fake. You encounter reflections in streams brighter and more saturated than the sky being reflected, for example. The posthumous PS candying of his images only made things worth. Only briefly, when his images were being handled by a true PS guru in this area, did his big inkjets look somewhat realistic, though I never found the fit of tiny 35mm originals to big prints to be a very comfortable one. His workshops basically taught machine-gunning : shoot and bracket as much as possible to get results. Why on earth anyone would take someone like that as model of metering proficiency escapes me. He was a traveler, an explorer who went interesting places, suitable as NG documentary fare. A skilled craftsman he was not, not even close. It was a marketing myth, an assumed persona, and he knew it too.

[Pere Casals]

probably seen Galen's pictures only in books - relatively tiny images.

35mm film is not for monster prints...



when more than one lab owner was complaining about NOTHING being in the shadows in his printed enlargements

Perhaps the printer you mention was speaking about this silhouette in the front cover of "Mountain Light: In Search of the Dynamic Landscape"

187384

Yes, a shadow impossible to print...




His workshops basically taught machine-gunning : shoot and bracket as much as possible to get results. Why on earth anyone would take someone like that as model of metering proficiency escapes me.

Well, nothing wrong in to advice bracketing in a 35mm workshop, bracketing is a good way to learn, in special with the small format. So this is the way: guess the right exposure but also bracket, then learn why you were wrong if you were.

[Alan Klein]

35mm film is not for monster prints...




Perhaps the printer you mention was speaking about this silhouette in the front cover of "Mountain Light: In Search of the Dynamic Landscape"

187384

Yes, a shadow impossible to print...





Well, nothing wrong in to advice bracketing in a 35mm workshop, bracketing is a good way to learn, in special with the small format. So this is the way: guess the right exposure but also bracket, then learn why you were wrong if you were.

I bracket my Velvia 50 120 Mamiya RB67 6x7 shots all the time. It takes another 5 seconds. It's easy to make a mistake when reading exposure off a reflective meter. Especially when you're shooting at magic hour when the light is changing so quickly and the light is so dramatic. Also, you might get a shot that jumps out when you bracket; one that you didn't predict. I can't pull or push the film. It's roll film that I have developed outside. Also, who verifies each of the Mamiya built in shutter speeds in each lens at each speed to verify accuracy? By the time you check your check sheet and adjust the shutter to true speed, the light has passed and you missed the shot. Better off bracketing.

Additionally, viewers don't care how many shots it took or if you got frostbite getting it. They're only interested if it's a winner when they view it. When you introduce your wonderful wife to others, do you mention how many losers you dated before you met her?

[Drew Wiley]

Do you practice that methodology with an 8x10 camera? In which case, you must need to have an elephant and mahout as assistants carrying your motorized 8x10 with all the necessary multitude of holders, and a commensurate monster budget. In those rather few cases I carried Velvia, it was likely a single holder for an entire trip. I had more versatile films, including black and white in the other holders. I could be a bit more generous in 4x5. But I necessarily allowed only one shot per subject. No room for error, no room for guessing, no opportunity to bracket, even if the light held steady. And what I've discovered is that a sniper with a single bullet is far more likely to hit a significant target than some machine-gunner who aims his gun all over the place. Even as a kid owning nothing more than an early 35mm Pentax with a single lens and rather crude externally coupled meter, I learned to do it right the first time on Kodachrome. Almost never an off exposure. Velvia was easy by comparison. But that doesn't mean Velvia is a versatile film. It has its legitimate usages. But most people simply want M&M brightly flavored candy, so that's why they use it. Galen was a nice guy just trying to make an honest living which supported his addiction to expeditions. I understand that. But being highly familiar with real mountain light, it's easy for me to smell something off which has been doctored up to exploit marketable stereotypes of natural beauty. Why gild the lily, or worse, dip it in melted M&M sauce? You're not going to improve it - you just cheapen that way! Burn all your damn postcards and cutesy nature calendars, leave your fancy cameras behind, and for once just sit there and watch what the light does, hour after hour in the mountains. Bathe in it, relish it. Maybe then you'll understand why I don't like hokey imitations. .... But no, I was not necessarily speaking of that specific cover image of Galen's, but of piles of them. Pretty much the same story. He had trouble with subject range, and depended too much on TTL metering. Again, I understand - it's kinda hard to use a real spot meter hanging from a rope. I doubt he even owned one. And sorry if I step on another set of toes; but more often than not, I regard resorting to grad filters as a default for not mastering the light to film ratio to begin with. Yeah, in color transparency work, where I began, the perimeter of the ball court tends to be significantly smaller than with black and white film. But in either case, it's essential to learn where those boundaries are. And that's why I'm perfectly comfortable going down to Zone I or even Zone 0 with certain black and white films, placing the beginning of shadow gradation way down there - because I had been routinely metering even more tricky things all along for sake of color chrome film. Don't tell me it can't be predictably done.

[Pere Casals]

Do you practice that methodology with an 8x10 camera?

No... but when learning how a film/process works I make bracketings with same film in 35mm... In particular I learned to meter/expose well velvia with 35mm bracketings. Characteristic curve in the velvia datasheet was wery good to understand the film, but also bracketings were essential to learn.

Also, while I may bracket a 35mm velvia shot, I don't bracket velvia sheets, instead I spend more time metering accurately. I guess that I'm not alone in that...

I've only one of the Rowell's books, here with with my very first 8x10 contact copy:

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Images are awesome to me, but also I've read all the book text, and I've to say that I learned a lot from that book.

[Bill Burk]

A friend of Galen Rowell's taught me snow skills. I never met Galen but I would have liked to. I read his articles and switched from Kodachrome to Velvia because of him. I never saw his slides. I have plenty of my own 35mm Velvia slides to live with. I know what they can do. Big pictures can be made from them. My buddy also shot Velvia, and he has a very nice large printed shot of his own on his living room wall.

When I took a nature photography business workshop in the late '80s I got to see some 4x5 color slides by William Neill. That was one of the moments when I decided to look into 4x5, as the saying goes... if two people walk into an editor's office with the same picture... the largest format is the one that will make the sale.

I respect those who want to take advantage of the inflection point, but it's probably clear by now that I prefer to be up on the straight line, and I use all this testing to determine an appropriate development time so I can print on my favorite paper, Galerie 2 or 3. And if I want to push the limits or be creative, I can do that too.

[Pere Casals]

About Rowell, it also has to be said that while ND graded filters had a limited use since the early twentieth century, he popularized the use of that resource in modern times.

[Drew Wiley]

Well, he certainly popularized the abuse of them.

[Pere Casals]

Well, he certainly popularized the abuse of them.

Well, what it's clear is that since then many nature photographers use that technique. Use or abuse, I'm not who would say it, to me this is about free people's personal preferences.

Rowell was clearly influential in the way high mountain photography changed, of course you are free to like or not his way, and to say it... But he was clearly influential, this is for sure.

[Drew Wiley]

He might have been a transient influence among amateur wannabee snapshooters and ski poster types, but he doesn't amount to a drop in the bucket if one considers all the serious mountain photography done beforehand, which has recognized worth and not just cutesy sugar-coated appeal. Nobody around here, right in his own back yard, took him seriously as a photographer, but did pester him like mosquitoes asking advice about their own expeditions, which he was competent to answer if he had to. I consider him an artistic zero, and rather unimpressive technically too, though that doesn't prevent me from appreciating the kind of Natl-Geo-ish journalistic applications his shots were appropriate for. I wouldn't have personally given him five bucks for any of them. Of course, I realize it's kinda rude to speak about someone who's no longer around and can't defend their reputation; but I don't think he even really cared about it except for its commercial utility. That whole "big photographer" thing was just an act, a persona. He actually seemed to be a bit embarrassed when around serious photographers - kinda humble in person in that respect. All the braggadocio in his articles was just part of commercial self-promotion. It only worked to a partial extent. His photography wasn't anywhere near as lucrative as some of him imitators imagine. He had other sources of financing. But if you like it, fine. I just think his kind of photography sets the bar quite low.

[Pere Casals]

Nobody around here, right in his own back yard, took him seriously as a photographer, but did pester him like mosquitoes asking advice about their own expeditions

Drew, I'm not interested in rivalities in a back yard, but in the global influence of a photographer.

Here you have an article by Tim Parkin (a member here, IIRC) and Joe Cornish about Rowell, please take a look, they are praising his work, contribution and influence:

https://www.onlandscape.co.uk/2011/01/master-photographer-galen-rowell/
https://web.archive.org/web/20190208084542/https://www.onlandscape.co.uk/2011/01/master-photographer-galen-rowell/

Drew, I don't say you have to value or not Rowell's work and/or contribution, this is up to you. But you should know that at least this article (by IMHO two prominent Landscape photographers) shows very different opinions than you.

I agree that he is not a "fine art" LF photographer, but a 35mm SLR adventure photographer. But by no means a photographer is more or less serious because of that.

So you can opine that Rowell's work is pest, of course, but by no means you can say that everybody here (or around) think the same. I fact if you dig a bit you'll find that remarkable photographers find themselves influenced by Rowell.


Joe Cornish: "Had he lived, Galen Rowell would by now be 70 years old. That his name still resonates down the years says much for the power of his art. I still remember finding Mountain Light at Stanfords, Covent Garden, on a grey London day in 1986. The colour and compositional invention and energy compelled me to buy, even though £25 was a lot of money for me. Twenty five years ago! I was lucky if I made £100 a week then. I read the text, every word. Several times (I made sure I had my moneys-worth). Along with David Muench's Nature's America, Mountain Light was my main inspirational, practical and conceptual resource for many years after."


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(Cornish with a graded ND filter)

[Alan Klein]

I'm curious of what those who use Velvia do with the film afterwards? Do you print it? How? What issues arise from exposure differences from "perfect"?

With my 120 Velvia 50 shots, I use to have an outside printer do it. They used C prints back then from an internegative. Now I'm only scanning and posting on the web. So my scanner and post processing programs can play with the exposures (I do bracket the shots when taking as well).

[Pere Casals]

I'm curious of what those who use Velvia do with the film afterwards? Do you print it? How? What issues arise from exposure differences from "perfect"?

With my 120 Velvia 50 shots, I use to have an outside printer do it. They used C prints back then from an internegative. Now I'm only scanning and posting on the web. So my scanner and post processing programs can play with the exposures (I do bracket the shots when taking as well).

Alan, today best bet is scanning and digitally printing on color photopaper with frontier, lambda, lightjet, etc, or the like, if not wanting inkjet.

[Drew Wiley]

Pere, if you fished around this forum a little more yourself, you'd discover that my opinions aren't unique, and might be even a little understated. People can adopt any role model they wish. But if you limit your selection just to Shetland Ponies endorsed by web jockeys, you're not going to win many real horse races.

[Drew Wiley]

Alan - Its perfectly feasible to make very high-quality internegatives on Portra 160 sheet film (via basic supplementary unsharp masking in cases of high contrast originals). Yes, this takes some practice and experience just like every other kind of darkroom work where quality results are the objective. But if one does take this route, they'll soon discover that the dye incompatibility as well as contrast issues of Velvia makes it particularly annoying to work with, that is, in comparison to tamer E6 films like Ektachrome, Astia, Provia, etc - just about anything other than Velvia. Then you'll probably also hear some nonsense about all that extra range in the shadows that can be recovered by scanning Velvia; but there's a catch to that - you're going to get a lot of oversized blue-biased grain down there, which isn't worth much in an actual print; it's generally better just to let it go solid black. But in this day and age if one wants something commercially printed from a chrome in other than inkjet, then some kind of laser exposure device like those mentioned already would be the realistic path. Labs these days aren't really set up to do internegatives anymore. And most of them never did it well to begin with. Like I stated earlier, pray for the return of Kodak E100G.