How to Develop Characteristic Curves in Large Format...Cheaply

I'm looking for a Densitometer at the moment and I'd like to get my zone system/sensitometric curves for my 8x10 camera locked down. Admittedly I haven't done this since college, and even then I did so with a roll film camera. At that time, I recall shooting a grey card over all 10 zones and reading the negs with a densitometer. This was after a test to establish my real ISO. (Forgive me, I'll be going back to my notes soon so I have the actual instructions as it's been a while).

The thought of burning through 10 or more sheets of 8x10 HP5 and FP4 or Delta sounds...expensive. I suppose I could get a 4x5 reducing back to save some $cratch but still...is there a more affordable way of doing this? I do recall having trouble with doing multiple exposures on a single sheet in college...

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Originally Posted by sperdynamite

I'm looking for a Densitometer at the moment and I'd like to get my zone system/sensitometric curves for my 8x10 camera locked down. Admittedly I haven't done this since college, and even then I did so with a roll film camera. At that time, I recall shooting a grey card over all 10 zones and reading the negs with a densitometer. This was after a test to establish my real ISO. (Forgive me, I'll be going back to my notes soon so I have the actual instructions as it's been a while).

The thought of burning through 10 or more sheets of 8x10 HP5 and FP4 or Delta sounds...expensive. I suppose I could get a 4x5 reducing back to save some $cratch but still...is there a more affordable way of doing this? I do recall having trouble with doing multiple exposures on a single sheet in college...

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You can do it with a single sheet by using a zone board. Notes for zone board construction and use are given in "The Book of Pyro" by Gordon Hutchings. (EDIT: To be clear, you'll need to burn at least one sheet for each curve required, i.e., one for your normal curve, another for your N-1 curve, another for your N+1 curve, and so on.)

N. Riley
http://normanrileyphotography.com

Years ago I used to test 8x10 films by doing stepped exposures by means of advancing the dark slide a little bit between shutter clicks. It's not hard to put 10 or more exposure steps along an 8x10 sheet. Keep exact notes. Then in the darkroom I would cut the exposed sheet lengthwise into four strips. All 4 strips go into a tray of developer at the same time but come out, one by one, at different times and go into the stop bath. When the last strip is stopped they all go in the fixer. The result is a one sheet film test with many exposure steps run at four different developing times - just about all you need to know about a particular film and developer combination.

After doing a lot of testing I've come to the conclusion that with modern materials, particularly since superb variable contrast photographic paper has become available, negative exposure is not critical as long as it is enough. Development is not critical either as long as it is enough. The challenging part is the constant search for expressive subject matter and the exhausting logistics of getting a 8x10 camera in front of it.

In my hands, the 35mm Hp5 results match 8x10, so I don't specifically have a need to test 8x10 sheets any more. But, when first starting out in 8x10, I did cut some 8x10 sheets in to strips to fit my sensitometer.
Attachment 196085

In "Beyond the Zone System" Phil Davis calibrated sheet film by contact printing a transmission step tablet with a single exposure. These can still be had from Stouffer for not-outrageous prices.

I use 4x5 film of the same brand as 8x10 and a dark slide cut in half. One side is Zone VII, the other size is Zone I. Zone I sets the film speed at 0.1 density units above film base plus fog. Zone VII sets the development time required to achieve a density of 1.15 above fb+f.

L

I'll suggest an alternative approach.

Forget the densitometer. Sure, it's great to quantify your data, but given the variables in the whole system with real-world subjects compared to test subjects (camera flare, meter flare, differences in meter response with varying light levels, densitometer errors, etc., etc.) your carefully-measured values are only likely to approximate real-world practice anyway.

So, save the money spent on the densitometer and do the following (keeping careful notes, of course):

Rate your film 2/3 stop slower than box speed.

Go out and find a "normal" subject for you, one that meters with low and high values where you want them on the Zone scale (or whatever other scale you use - I'm a Zone System user).

Shoot two or three identical negatives of your chosen scene.

Develop one at your best guess for your Normal development time in the developer of your choice.

Print your negative. First, make a contact print with minimum exposure to get the film rebate to print very close to the maximum black the paper can deliver. This is a "proper proof" and gives information on exposure.

Evaluate this print carefully. Compare blacks in the print to the black in the rebate. Is the shadow detail what you metered/expected? Where do the highlights fall, i.e., do they correspond to the metered values? This information will help you make adjustments to your exposure and development later.

So, if your desired shadow detail is lacking, you've underexposed. This, however, is highly unlikely, since you've rated your film 2/3-stop slower than box speed. What you may see is potential to rate your film a bit faster, but I'll wager you'll be well in the ballpark as far as exposure goes. Erring a bit on the side of overexposure will give you a very printable negative. You can refine your personal E.I. on the next trip out.

Don't worry about any of that now, however. Go back and make your best print at whatever exposure you need to get good shadows, but avoid manipulations. This is your "straight print" and it gives information on development.

Now it's time to evaluate the highlights. It's the highlights that will help you with development. Blown out? The negative is overdeveloped. Too muddy? The negative is underdeveloped. Just right? You lucked out and have found a usable Normal development time.

If you do need to adjust development time, now is the time to dig out those other negatives you made. A 20-25% change in development time equals (very) roughly a paper grade or N+, N- change, so decide which way you want to go (longer or shorter development) and how much you want to change (15% = half a Zone or thereabouts).

Develop the next negative and evaluate it as above.

By now, you're going to be close to finding a usable Normal development time and personal E.I. for your film/developer combo. And, you'll likely be well within the possibilities for contrast adjustment offered by the papers today. Sure, you can keep tweaking, but remember, you only need to get close to the middle of the paper-contrast range and make sure you have enough shadow detail for your taste in order to make a fine print. The rest of the art lies in finding something to point your camera at.

Repeat this process for contrast expansions and contractions. With expansions, you won't have to worry about changing film speed; a bit more exposure won't hurt. With contractions, you'll want to give more exposure, since developing less slows the film down a bit. Start with 2/3-stop per Zone of contraction (this may be too much, but better too much than too little). Find you N+ and N- subjects and make three negatives, just as above and print two versions of them, as above. Use 20-25% change in development time from your Normal time as starting points and proceed as above, but figuring in the highlight displacement.

Before long, you'll have a whole stable of possibilities, all without a densitometer.

Have fun,

Doremus

Although not the system I use, Doremus idea is a very good one,and practical.

The OP asked about curves. From my perspective, this is the special value of a densitometer. You don't need one to figure out how to expose adequately for the shadows or how to develop to keep the highlights under control. But if you are relatively new at this game, running a step tablet is the most efficient way to understand the shape of the characteristic curve that you get from a film/developer combination - and, in turn, to predict which papers will render your negatives with the tonal distribution you prefer.

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Originally Posted by Oren Grad

The OP asked about curves...

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Oren,

I got the impression that the OP was really interested in establishing E.I. and development times. If, indeed, the OP is interested in sensitometry and plotting curves, then a densitometer and step tablets (calibrated) are going to be indispensable.

Best,

Doremus

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Originally Posted by sperdynamite

I'm looking for a Densitometer

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While you dont have it...

just scan (16 bits per channel) an stouffer T2115 transmission wedge alongside with your negative, at the same time with all image enhancing disabled, then in Ps just compare the gray values in a spot in the gegative with the patches in the scanned wedge.

perhaps not as convenient than a densitometer, but perfectly accurate. I've a densitometer but I use that way.

Poor man's densitometer : Take a sheet of black cardboard and an ordinary hole punch. Punch the holes a few inches apart. Place your step wedge atop a light box adjacent to the sheet film neg you're trying to measure, then the black cardboard atop both. One hole should be over the part of the negative you're trying to read, and then shift your step wedge until the patch on it which most closely visually matches the area on your neg matches. It's called visual densitometry, and is quite adequate for basic purposes or elementary plotting, including the Zone System. For high-quality plotting, get a real b&w transmission densitometer and appropriate graphing sheets, or else a program that accepts your reading and plots the curve for you.

In graduate school, before I obtained a real densitometer, I placed my samples between my spot meter and a light bulb to make the H&D curves. When I got a 'real' densitometer, the curves I made were pretty much the same.

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Originally Posted by ic-racer

In graduate school, before I obtained a real densitometer, I placed my samples between my spot meter and a light bulb to make the H&D curves. When I got a 'real' densitometer, the curves I made were pretty much the same.

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Phil Davis's BTZS book, or at least the third edition which I have, has an appendix with some guidance on using a spot meter as a makeshift densitometer.

Also... On a light table, we may check exposure with the spot meter of a dslr in a point of the negative, and later finding the matching patch in the Stouffer, also with the spot meter.

The worst thing to no information is incorrect information. Use a densitometer!

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Originally Posted by Luis-F-S

The worst thing to no information is incorrect information. Use a densitometer!

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This is very good advice, no doubt.

Anyway let me point that the greatest errors sometimes come from the best instruments.

Today we can access used great densitometers at low price, I got my very good one for $25, but the important thing both in new and used gear is checking accuracy.

Fortunately we may use calibrated wedges that allow to check used and new gear, and very pro or DIY made devices.

As always in any kind of lab, it is important to check accuracy in instruments because a reading is never perfect, and even a very good instrument may end in a pitfall because some dirt is in the sensor.

A Calibrated wedge (or even a regular one) it is what in fact what we need to know what we are doing.

I thought I'd pitch my book... I think I've sold one copy. Oh yeah I didn't really sell it. One day a Photrio member 'peoplemerge' came by my local coffee shop and I gave it to him along with a GE light meter. Yes you can make a densitometer out of a GE light meter.

http://beefalobill.com/imgs/20150812...dAttention.pdf


Here's an excerpt from the book relevant to this thread... echo's of Pere Casal's advice... buy a T2115 for the price of one sheet of film. If you like get the calibrated T2115C for about the price of three sheets of film.


Recommended: Stouffer Step Wedge T2115
( http://www.stouffer.net/TransPage.htm )
You can set this scale on top of a piece of film, cover it with a piece of glass, as for contact printing, and
expose under an enlarger. Although this isn’t highly accurate, it is easy to setup and will be much better
than most other test methods. There are two important flaws in the test: reciprocity law failure may
occur due to a few seconds exposure and the light source of the enlarger is different than the spectrum
of light you would probably use when taking pictures. The advantages of contact printing outweighs
the significance of these flaws.