Under versus Over (Exposure & Developing)

Papa Tango · Apr 14, 2006

Not to get into a really technical N+ debate here, but I am confused. Underexposing a negative will result in a "thin" (lighter) negative with soft contrast loss in all ranges. Overexposing will result in a "thick" (darker) negative, with increased shadow detail and brighter highlights first. Correct?

Now lets say that we are developing a "perfectly" exposed negative. From what I am reading, underdevelopment will result in a "thin" (lighter) negative with less contrast, and overdevelopment a "thick" (darker) negative with stronger contrast?

Having never varied too much from the recommended development times, I have no practical experience that observation would answer this. Some sort of "common sense" tells me that underdeveloping would make for a dark negative, and overdeveloping for a light one. Or is this something that is variable depending on whether a solvent or acutance developer is used?

reellis67 · Apr 14, 2006

The best example of this that I have seen is in this book

http://www.amazon.com/gp/product/15...=pd_bbs_12/104-0153450-2704762?_encoding=UTF8

Creative Black and White Photography. There is a chart showing the same scene shot under and over by varying amounts and then developed over and under, in a more scientific way than I have described here, so that you can see the whole range of results from under/under to over/over and all steps between. It is a nice, concise, visual example of results that make it much easier to understand, for me anyway.

- Randy

Donald Miller · Apr 14, 2006

Pragmatist said:
Not to get into a really technical N+ debate here, but I am confused. Underexposing a negative will result in a "thin" (lighter) negative with soft contrast loss in all ranges. Overexposing will result in a "thick" (darker) negative, with increased shadow detail and brighter highlights first. Correct?

Now lets say that we are developing a "perfectly" exposed negative. From what I am reading, underdevelopment will result in a "thin" (lighter) negative with less contrast, and overdevelopment a "thick" (darker) negative with stronger contrast?

Having never varied too much from the recommended development times, I have no practical experience that observation would answer this. Some sort of "common sense" tells me that underdeveloping would make for a dark negative, and overdeveloping for a light one. Or is this something that is variable depending on whether a solvent or acutance developer is used?

You are correct that underexposure would lead to a thin negative and a thin negative will print darker, all things being equal. By the same token underdeveloping a negative will also lead to a thin negative and it will also print dark.

Over exposure will lead to a denser negative and the denser negative will print lighter, all things being equal. By the same token over developing will also lead to a denser negative and it will print lighter, all things being equal. However in the case of over developing we will typically expand the exhibited density range of the film and it will exhibit greater contrast when printing.

The other considerations that become involved are these. If a negative is underexposed sufficiently then no amount of development will make a denser negative of it. By the same token if a negative is over exposed then it will exhibit greater low value density then a perfectly exposed negative.

What this translates to is that if one sufficiently overexposes a negative then the negative will be compromised to some extent, depending on the degree of over exposure, in it's ability to exhibit it's full potential of density range. The gamma infinity (ability to build density range or contrast) is a fixed quantity no matter whether you develop the film for 15 minutes or fifteen days. In fact over development at some point becomes counter productive because one builds overall density and the density range or contrast of the negative may actually decrease. Of course there are differences in films. For instance Bergger BPF 200 is noted for it's inability to produce a higher density range. Whereas Tmax 400 and Efke are noted for their ability to build higher density ranges.

I hope that this answers your questions. Good luck.

Photo Engineer · Apr 14, 2006

I almost always overerexpose by 1/3 stop and develop normally. This keeps the image still on the straight line portion of the curve by not being a severe overexposure, corrects for any possible mistake I might make, yields negatives that are not too dense, and gives normal contrast.

It has always seemed to be the best of all possible worlds.

PE

Papa Tango · Apr 14, 2006

Donald, that is pretty much what I was looking to confirm. What happens with the exposure of the film is something that I am experimenting with, specifically lowering the rated ISO and developing accordingly.

I have had it stuck in my mind for many years that overdeveloping led to thin negs simply because the developer removed all the silver. Dont ask where this foggy gem came from. One of the reasons I am working through all of this is that I am finding that with slow films such as Efke 25 and Ilford Pan-F, going the standard recommended development times is leading to "thinner" negatives, in some cases bordering on unusable. This has been with D76 1:1. I am moving away to Rodinal stand dev with the Efke, as the results I am getting are expected and satisfactory. I was uncertain with the Pan whether I should extend or reduce dev time.

I eliminated metering and shutter speeds some time ago from the equation, and found it to be centered on development. On to some test strips...

Papa Tango · Apr 14, 2006

PE, I have been doing something similar for many years. By reducing the effective rated ISO and developing normally, I routinely get the results I am looking for. But these two slow films have been confounding me...

Allen Friday · Apr 14, 2006

I think that being able to judge the exposure and development of a negative is an important skill to acquire. It will aid you greatly in printing later on. I also think it is very hard to learn from reading about it or from descriptions of other photographers. I recommend that you "waste" a roll of film and see the results for yourself.

All you need is one roll of 35 film. Shoot the entire roll in sequence: 1. at the meter reading, 2. two or three stops over meter reading, 3. two or three stops under meter reading. (Repeat). In the dark room, develop the first third of the roll for 1/2 your normal time, the middle section at the normal time and the last third at twice your normal time. Once dry, compare on a light box and try printing. You'll see the difference, I guarantee it.

noseoil · Apr 14, 2006

Patrick, you have asked a very good question, one example you have given merits a bit more explanation here. If you have underexposed, let's say a half stop just to pick a number, there are a couple of things to consider. Your range of values will have "shifted" to a lower value in general. Given "normal" development, this film will show more contrast, only because the normal shadow values will have now fallen below the threshold of detail. This will make the "apparent" range of values seem to be pretty contrasty in the print. No amount of printing manipulation will give detail where there is none on the film. Your high values can be brought out, but by the time you have done this, the deep shadows will be empty and black. The result is a print in which there are highlights, but the shdows look pretty heavy (an example using graded paper, not variable contrast).

In a normal film, you will have nice tonality throughout the scale you want to show in the print. Once you have found the correct exposure and development, there is a consideration to make about the high values. Do you want to increase development a bit, just to make the highlights sparkle? Do you want to leave them alone so they are "just right" as they are? There is no correct answer, so the amount of development will vary from scene to scene, depending on how you see, print and feel about the light, etc. tim

gainer · Apr 14, 2006

The effect of changes in development as well as changes in exposure depends on the shape of the film's characteristic curve. We have films with a gradual upsweeping curve, films with curves that are nearly straight lines, films with S-shaped curves, and everything between. A change in exposure does not change the contrast of a film as long as the exposure range lies within the straight part of the curve, if it has one. In any case, the effect of change in development cannot be guaranteed to produce the same effect as a change in exposure. A change in exposure of a film with an upsweeping curve will produce a change in contrast, but it may not look like the same film with a change of development, and it may be better or worse for the situation at hand than a change in development. Rules of thumb are only adequate for guiding experiments. One learns this fact least painfully by doing the experiments before using rules of thumb to guide important work. I have bruises all over my ego.

j-fr · Apr 14, 2006

Pragmatist said:
Now lets say that we are developing a "perfectly" exposed negative. From what I am reading, underdevelopment will result in a "thin" (lighter) negative with less contrast, and overdevelopment a "thick" (darker) negative with stronger contrast?

The negative is always the result of both exposure and development. If the balance is correct, you get a correct negative, providing the contrast in the subject suits the contrast in the process. By balancing exposure and development you can get exactly the contrast that fits the subject. To put it very - too? - simple. So a "perfectly" exposed negative needs a "perfect" development.

j-fr · Apr 14, 2006

gainer said:
The effect of changes in development as well as changes in exposure depends on the shape of the film's characteristic curve. We have films with a gradual upsweeping curve, films with curves that are nearly straight lines, films with S-shaped curves, and everything between.

No, that is not correct, sorry to say. Films will in some developers come out with an upsweeping curve but in other developers they give straight or even a s-shaped curves.

So the shape of the curve is not a characteristic of the film. It is a characteristic for a specific combination of film and developer.

dancqu · Apr 14, 2006

Pragmatist said:
Underexposing a negative will result in ...
Overexposing will result in a ...

Exposure creates a potential for image formation.
Development creates the image.

It's all about creating a correct potential image
at time of exposure then developing that image to a
correct range of densities. The correct range of the film's
developed density is to equal some paper's exposure vs
density response. The proof of all that pudding ends
up on a sheet of paper.

Of course "correct" is in the eye of the beholder. An
arty type may just say "screw all that". Dan

gainer · Apr 14, 2006

j-fr said:
No, that is not correct, sorry to say. Films will in some developers come out with an upsweeping curve but in other developers they give straight or even a s-shaped curves.

So the shape of the curve is not a characteristic of the film. It is a characteristic for a specific combination of film and developer.

I don't know how many such curves you have seen with different developers. Phil Davis did an extensive set of curves of different films and different developers some time ago for Darkroom and Creative Camera Techniques, now known as Photo Techniques. The question as I saw it was not what happens when you use different developers, but what happens when you expose differently and when you develop differently, and I figured the questioner was planning to expose one film and use one developer. The comment still applies, however, that you cannot depend on experience with one combination to establish rules for another combination.

j-fr · Apr 15, 2006

gainer said:
I don't know how many such curves you have seen with different developers. Phil Davis did an extensive set of curves of different films and different developers some time ago for Darkroom and Creative Camera Techniques, now known as Photo Techniques. The question as I saw it was not what happens when you use different developers, but what happens when you expose differently and when you develop differently, and I figured the questioner was planning to expose one film and use one developer. The comment still applies, however, that you cannot depend on experience with one combination to establish rules for another combination.

I have seen - and drawn - quite a lot of curves. And, most important, I've used the information from my tests to make pictures.

Here's a challenge: Take a film, T-MAX 400 for example. Expose a couple of rolls or sheets and develop one in T-MAX RS and the other in D-76, not to mention other and more exotic developers. Compare the curves and try printing the negatives. You will then find that curves that to a superficial glance might look the same, really are very different.

As for Phil Davis and his findings and writhings I would rather not comment. Only this: His book "Beyond the Zone System" is probably the worst ever published on a subject that has seen many strange publications over the years.

It is a very good idea to use one film, one developer and one combination of exposure and developing. Most work can be done that way. The question of course is: What combination and how to find it?

gainer · Apr 15, 2006

Please don't change the subject. I said nothing about Phil Davis' book. I have not read it. It has no bearing on the veracity of his test results, and neither do your opinions of his method or book. Data are data. Families of characteristic curves can only be criticised on the basis of equipment or technique in using it.

The subject at hand is to compare what happens when one changes development with what happens when one changes exposure. Nothing was said about comparing different combinations of film and developer. I have done a lot of that in my 65 years of developing film, and I can say that my experience has taught me that you cannot reliably get the same results from changing exposure that you get from changing development.

Bruce Watson · Apr 15, 2006

I'm going to throw in my $0.02 just to add a different perspective.

The combinations one can get by varying exposure and varying development, for a given film and a given developer, are larger than they might first appear. Exposure and development seem to work together but in fact work differently and are not symmetrical. That is, if you expose and develop normally, then overexpose by 1/3 stop and underdevelop by 1/3 stop, you don't really end up in the same place like you'd think you would.

Think of it like this. Exposure for a given film determines where the image is going to be along the characteristic curve. This is particularly important at the toe of the curve. If you expose too little, you don't create a latent image since that data falls below the toe of the curve. If you expose more, you move the image up along the curve and pull shadow detail up over the toe. Thus the admonition "expose for the shadows."

Development determines maximum density and thus the slope of the characteristic curve (some call this the gamma, some call it the contrast index). Development doesn't move the image up or down the characteristic curve - it merely changes the slope of the curve. Thus the admonition "develop for the highlights."

Now if you want to really get into it, you'll need a establish some sort of methodology. That is, something like the Zone System. I personally like the Zone System, and suggest that anyone really wanting to understand how exposure and developing effect film should read the Adams book The Negative. It's a fairly stiff read, and there are therefore many books that cover much the same material in different ways. You need to find a book that explains it to you in a way that you like. So clearly, YMMV.

Stephen Benskin · Apr 15, 2006

j-fr said:
I

As for Phil Davis and his findings and writhings I would rather not comment. Only this: His book "Beyond the Zone System" is probably the worst ever published on a subject that has seen many strange publications over the years.

I'm curious why you think this. I find Davis' sensitometry to be solid and his grasp of tone reproduction is strong. He doesn't go into enough detail on some subjects; however, which I feel can lead to misunderstandings. The other aspect of the book, his system, is another matter. I personally like to use more of a straight form of tone reproduction.

What aspects are you referring to?

Steve

j-fr · Apr 15, 2006

Well, maybe we should start a new thread; we're now a rather long way from the original question.

But, in brief:

Phil Davis is making things extremely complicated. One of the most basic matters: that curves come in different shapes, must have escaped his attention. As so many other zone-system proponents he seems focused on the idea that it is possible to make all films & developers to behave in the same way: N, N+1, N-1 and so on. But only a few can do it.

It is a long and complicated discussion that also includes a proper definition of film speed, paper characteristics and much, much more. But it has to do with the very basics of photography.

By the way: What is this more straight form of tone reproduction that you prefer?

Photo Engineer · Apr 15, 2006

I have been following this discussion with quite a bit of interest as there is two big points that everyone is missing in this side topic or digression.

It is correct to say that films have all types of curves, from straight and long to short and bowed. It is also correct to say that different developers yield different curves with each film.

What is missed here is first that a long straight curve may vary a lot from developer to developer, but on average it will retain its main curve characteristic of being long and straight when compared with the other films similarly tested.

Second, and this was alluded to by J-FR that two films in one developer, or one film in two developers may have nearly the same shape but yield different results when printed. Now, this is the key to the whole thing, and it is a topic being ignored repeatedly on all photo forums that I have visited.

There is a MACRO characteristic curve and a MICRO characteristic curve. These can vary based on edge effects. We commonly only measure the macro curve. The micro curve requires a micro-densitometer for measurement and requires knife edge exposures of different densities for this measurement. The micro curve of a given film in a given developer may vary for 35mm images, 120 images and 4x5 images from the same film and developer combination, or they may vary over one film in several developers at one magnfication, but they may all give the same macro scale.

This is critical to understanding what J-FR said!

The result is that you can have two identical curves which yield different results when printed. It is not always true, but more often true than not, and never ever discussed here on APUG or elsewhere.

There was a thread here, I believe started by Kirk Keyes some weeks ago. He is making exposures on definition charts to test the resolution of some films. His tests may be able to illustrate some of these points when he is finished.

For the most part though, comparing developers and macro curves is somewhat futile unless you are able to compare image structure, otherwise, as J-FR says, the curves are almost identical but the images look different. This statement can be measured and made more reassuring than its qualitative nature, I assure you. I hope that I can get someone interested in making this critical type of measurement.

PE

j-fr · Apr 15, 2006

Photo Engineer said:
There is a MACRO characteristic curve and a MICRO characteristic curve. These can vary based on edge effects. We commonly only measure the macro curve. The micro curve requires a micro-densitometer for measurement and requires knife edge exposures of different densities for this measurement. The micro curve of a given film in a given developer may vary for 35mm images, 120 images and 4x5 images from the same film and developer combination, or they may vary over one film in several developers at one magnfication, but they may all give the same macro scale.

Now this is very interesting! Before I post a more comprehensive answer (maybe in a new thread?) there is one question that is important:

Will a certain measured density always yield the same grey-tone when printed? Or could some "micro curve characteristic" or something else imply that a certain measured density of say 0.50 prints a one grey tone and another measured density of 0.50 prints as another (slightly?) different grey tone?

Photo Engineer · Apr 15, 2006

j-fr said:
Now this is very interesting! Before I post a more comprehensive answer (maybe in a new thread?) there is one question that is important:

Will a certain measured density always yield the same grey-tone when printed? Or could some "micro curve characteristic" or something else imply that a certain measured density of say 0.50 prints a one grey tone and another measured density of 0.50 prints as another (slightly?) different grey tone?

Unless there are absolutely no edge effects whatsoever, and the film/developer combination yields identical macro and micro scales, then a macro measurment of 0.50 may print differently when printed from a 1000 micron line, a 100 micron line, a 10 micron line and a 1 micron line. The densities of these lines will be altered to the extent that there is an edge effect, and they will not be equal to 0.50.

PE

dancqu · Apr 15, 2006

gainer said:
...my experience has taught me that you cannot reliably
get the same results from changing exposure that you
get from changing development.

I wouldn't even try. How could any one expect to. Dan

Stephen Benskin · Apr 15, 2006

j-fr said:
Well, maybe we should start a new thread; we're now a rather long way from the original question.

But, in brief:

Phil Davis is making things extremely complicated. One of the most basic matters: that curves come in different shapes, must have escaped his attention. As so many other zone-system proponents he seems focused on the idea that it is possible to make all films & developers to behave in the same way: N, N+1, N-1 and so on. But only a few can do it.

It is a long and complicated discussion that also includes a proper definition of film speed, paper characteristics and much, much more. But it has to do with the very basics of photography.

By the way: What is this more straight form of tone reproduction that you prefer?

Let's do it and start a new thread. There are some interesting ideas in which to pursue here. Film speed theory is one of my favorite subjects, and I've just finished a manuscript on film developmental models (what is N, +1, etc). Since you have some definite ideas about Davis, please take the lead and present your thoughts.

When I say straight, I mean without (and I can never think of the right term) tricks, systems, gimmicks placed on top of it. IMO, when you create a system, you need to simplify concepts, and that leads to problems.

Steve

gainer · Apr 16, 2006

What shall we call the thread so I will know what to look for?
There are indeed many things to deal with.
Phil Davis, from what I have read of his writings, did NOT assume that all films could be made to print the same. He wrote another article for P. T. in which he demonstrated that simply matching the density range of a negative to the density range of a paper would not always produce the same visible result. The same applies to any system of matching, zone or otherwise. This problem was recognized before the book "Principle of Optics" by Hardy and Perrin, 1932, was published and was discussed therein. Unless the characteristic curves of film and paper are complementary, the print will be distorted from a true representation of the original scene. It is not necessary in theory that both be straight lines, though that is one case of complementarity.

Photo Engineer · Apr 16, 2006

Patrick, it has been shown by a number of modern workers that the curve of the final print is the product of the film and paper curve. It is more complicated than that, in that it involves calculus and matrix algebra if you wish to compensate for spectral sensitivity of the paper and the tone of the developed silver, as well as correct for micro vs macro contrast.

The most significant contribution comes from the micro contrast curve, but the measurement of micro contrast must be done as a function of magnification, as the final result will be seen to vary as magnification changes.

There is an article by M. Kriss that covers this quite well. Figure 5-10 shows variations in contrast as a function of chemical adjacency effects from 1000 microns down to 10 microns.

PE

Under versus Over (Exposure & Developing)

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