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.
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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.Quote:
Originally Posted by IanBarber
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 outQuote:
Originally Posted by Larry Gebhardt
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.Quote:
Originally Posted by IanBarber
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 :)
Attachment 186694
Go back and read my post, Ian!Quote:
Originally Posted by IanBarber
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.
The flaw is not explaining how true film speed is calculated...Quote:
Originally Posted by Drew Wiley
This is a number, tell me, how do we caculate it?
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.
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...Quote:
Originally Posted by Drew Wiley
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.
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
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.
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.
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)
Yes, x10 is what is the exact definition... from 3.3 to 3 1/3 we have a 0.033... differenceQuote:
Originally Posted by Bill Burk
Bernard, the 3.3 vs 4.3 issue comes from the 1960 speed change specified in the American ASA PH2.5-1960 standard.Quote:
Originally Posted by Bernard_L
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)
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.Quote:
Originally Posted by Bernard_L
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...
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.Quote:
Originally Posted by Bernard_L
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_valueQuote:
Originally Posted by Bernard_L
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.
Pere, that is what you state in post #61.
[10x = 3.33 stops]Quote:
Bill, the true speed formula makes the meter aim to exactly x10 the exposure in the m speed point, this is exact.
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.Quote:
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.
What difference does it make if you never go and take photos because you’re glued to the computer!
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).
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).
Quote:
Originally Posted by Bernard_L
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...
Quote:
Originally Posted by Luis-F-S
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
This was a great post. I’d say the first choice was always the bestQuote:
Originally Posted by Pere Casals
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 !!!Quote:
Originally Posted by Bill Burk
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...
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.
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
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 ?Quote:
Originally Posted by Doremus Scudder
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.
Drew, you like linear films, so you won't have any problem...Quote:
Originally Posted by Drew Wiley
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?
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.
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?
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.
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.Quote:
Originally Posted by Alan Klein
Quote:
Originally Posted by Pere Casals
Pere,Quote:
Originally Posted by Pere Casals
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
Well, I also find funny discussing aganist myself !! :)Quote:
Originally Posted by Doremus Scudder
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...Quote:
Originally Posted by Doremus Scudder
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.
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.Quote:
Originally Posted by Doremus Scudder
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 !!!!
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.
Drew, what films/development ?Quote:
Originally Posted by Drew Wiley
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 ?
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.
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!
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).
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/Fic...ncro400_en.pdf,
Attachment 186969
https://www.largeformatphotography.i...=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/1/883/42...da866034_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...
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.
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 ?Quote:
Originally Posted by Drew Wiley
Tell me what's "using the entire curve" if you have a 8 stops range in the scene...
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.
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).
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...Quote:
Originally Posted by Drew Wiley
Interneg, a 2.8D negative with grade 2, with no extensive manipulation?Quote:
Originally Posted by interneg
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.Quote:
Originally Posted by Drew Wiley
This is a N-3 or beyond, and reaching 2.0D: https://www.flickr.com/photos/125592...posted-public/
I had made a N I would had "smoke" from the negative...
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.Quote:
Originally Posted by Pere Casals
Too often people get obsessed with opening shadows that should be dark...
Interneg is a user name not what we are making.Quote:
Originally Posted by Pere Casals
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.