exposure and tonality

[LoveMinusZero]

i hear that different films have different amounts of contrast, therefore different tonal qualities. so, how do you choose the tone you want when the same exposure will result in different tones for the same brightness levels? in terms of the zone system exposure, the meter's reading is middle gray, zone v, and each zone is one stop difference, so you adjust the number of stops to get to the desired zone. but, if films have more or less contrast, the tones must be different, and then apllying the zone exposure would not be effective, as different films might put the tone in zone IV rather than zone III.also, supposedly differing contrast developers pose the same issue. so, what is the solution to this problem? any input is appreciated, thanks

 

[noseoil]

Exposure and development

First, I prefer Joan Baez's rendition over Dylan's, but that is just a personal preference. Both are good versions. It is the same thing with the film / exposure / development rendition.

The first place I would start is with a test of materials, paper, film, developer etc. Ideally, you will have tested your film's printing on the given paper, so there is an understanding of exposure & development with respect to the paper. This is crucial to a discussion of exposure. Remember, the exposure is just one part of this whole process. It is the minimum amount of light necessary to hold firm shadow detail. The second part is the development of the shot. More development equals more contrast. Two different films can be made to print similarly on the same paper, but this is a relationship of development and the paper's contrast. By adding development time, highlights are made whiter, until they go off the scale and turn paper white.

I can give an example from a roll of film I took yesterday. The shot was done with Efke 100 and developed in pyrocat with minimal agitation. The film generally has a nice rendering of tones and a great ability to expand or contract as a result of development. The wagon wheel is white paint, but the wagon itself is bright red. With this film, red is seen as a fairly neutral gray. Efke 25, on the other hand, sees red as almost jet black (ortho-oanchromatic = doesn't see red as we do). This is the film's ability to see red, not the paper, developer or development. If I had used Efke 25 for this shot, the wagon in full sunlight would have looked dark gray (nearly black) and shadows on the red paint would have been depressed to about zone 0. No amount of tweaking during exposure, development or printing would have helped. This is a characteristic of the film, not exposure. To say we can change zones simply by exposure is a half truth for me. It is not the whole story.

When we place values on the zone scale, it is because we have tested the paper, film and developer to know where the placement of values will fall. Once the tests are understood, we can adjust these values to print an image in which tones are manipulated to be placed where we wish, instead of where they fall. If you are just starting out with this whole business, give yourself time to work with a single film, developer and paper. Too many variables can result in too much information which can't be understood easily. With roll film, try experimenting with exposure and development. Figure out a minimum asa for your film and use it. Then, play around with developemnt so you can see how one shot varies with respect to development. It takes some time for all of this to sink in. Do a half roll with one exposure, then the second half with the same exposure, but change development. Cut it in half and play with times. Welcome, tim

 

[rbarker]

I like the Baez/Dylan analogy. Joan Baez's rendition (of almost any song) is like a fine-grained print that has a full range of tones, while Dylan's style is more like compressing the contrast up toward the shoulder of the film's contrast curve combined with lots of coarse grain (i.e. his raspy twang).

In determining how to apply the concepts of exposure and development to a particular scene, whether via the Zone System or some other, it may help to think in terms of the contrast curve of the selected film. Assuming a scene with a full range of tones, "normal" exposure will place the negative in the center of the curve. Adjustments in exposure will move up or down on the curve, and changes in development will either compress or expand the contrast range in the negative.

The basic choice is whether to render the scene as it is, or to "place" the values differently by adjusting the exposure, and then potentially compensate with corresponding adjustments in development. A secondary objective in all of this is to arrive at some degree of consistency in negative density (mostly controlled by exposure) and some consistency in negative contrast (mostly controlled by development).

That's why "testing" (aka experimentation with) a specific film/developer combination is so important. That's the only way you can familiarize yourself with the characteristics of the combination, and how changes in exposure and development will translate in the resulting negatives. Once you know what is possible with that particular film/developer combination, you can apply that knowledge to choosing the most appropriate exposure and development for a particular subject or scene.

 

[LoveMinusZero]

thanks for the information. i'm still a bit puzzled with all of the variables of paper, film, devloper, time etc. i appreciate the analogy, and i understand the pefrsonal preference. i read an article at luminous-lanscapes.com about simply alter exposure one stop for each succesive zone, allowing each stop off the meters reading to be a zone up or down from zone V, assuming that the meters reading will always print neutral gray. but, i suppose simply changin the paper willl darken or lightren the tone.

is there any way to apply this system without printing your own work, jusat by developing it? can i have the lab use a specific grade of paper to print, or do they just use their own stuff?

 

[Alan Johnson]

"Beyond Basic Photography" by Henry Horenstein gives in Appendix 1 a film speed test that requires negatives only,no printing (You need a gray card and a wratten 96 0.1 neutral density filter though).
In Ch 1 is discussed how to change the exposure index for contrasty and low contrast conditions,or, if preferred,there is an introduction to the zone system. The development time will likely require changing. This testing may be carried out by photographing actual subjects and having the lab print the negs.They should be able to print on grade 2 or 3 paper if the exposure and development are good.

 

[Christopher Walrath]

Ansel Adams also has film testing data in his The Negative. And some shops might be willing to experiment with you for the right fee. Ask around and find someone you are comfortable with and they might just be willing to work with you to acheive the look you are searching for.

 

[LoveMinusZero]

thanks for the info, i think i have some understanding. the differnce in contrast depnds on where the developer puts the highlights, the shadows are pretty fixed with the exposure, no matter the developer, assuming you have the accurate film speed for the developer. whats the best way to find the ISO for a given film and ddeveloper combo?

 

[Alan Johnson]

The method described in Appendix 1 of Horenstein's book will give a film speed.It it usually called a personal exposure index,EI, and not ISO as it also depends on the accuracy of the meter, shutter and aperture settings.
An alternative I use is to take pictures out the back of the house under conditions I intend to take photographs (sun,shade). For 100 ISO film I set the camera ISO to 40,50,64,80,100,125,160,200, take one picture at each setting,develop etc,then hold the negatives up to the light and see which setting gives the amount of shadow detail I want.If the neg will not print on grade 2 or 3 it is necessary to try again with a different development time.This gives the EI for that film in that developer under those contrast conditions.The EI may be as low as 40 for Rodinal or as high as 200 for 2-bath developers, for 100 ISO film.

 

[noseoil]

Edit to my above post. Efke 25 is an ortho-panchromatic film. Sorry about the typo. tim

 

[LoveMinusZero]

wouldn't you need to photograph a shadow at a couple of exposures to find the EI, or else the development could overdevelop the highlights, even though you underexposed? also the same for midtones?

 

[Christopher Walrath]

There's a great article in UK-based Black and White Photography, Christmas edition, pp54-55 by Mike Johnston about an older still procedure refered to as the ring-around. Might be worth checking out.

 

[rbarker]

wouldn't you need to photograph a shadow at a couple of exposures to find the EI, or else the development could overdevelop the highlights, even though you underexposed? also the same for midtones?

Sorta, kinda, maybe.

Many testing methods lean toward "exposing for the shadows" to determine a personalized EI (adjusted ISO, recognizing that this is really a misuse of the term), with the associated concept of "developing for the highlights" - i.e. adjusting development to control the contrast range in the negative ("normal" contrast scenes get "normal" development, etc.). The problem, of course, is how one defines "shadow" - absent some predetermined control point - and what is "normal". Some sensitometry-based methods, for example, look for a certain increase in negative density above film base + fog (the density of the non-image areas of the developed film). Other methods take different approaches to accomplish similar goals.

My suggestion to beginners (particularly those who don't have a densitometer) is to pick a method that seems to make intuitive sense to them as an individual, and then work with it for a while. Over time, and with some experience under one's belt, other methods may become more attractive. That depends on how "scientific" one wants to be about the whole thing. Consistency in method, whatever it might be, is probably more important in the long run, however.

The other factor that plays into this is the dynamic range the particular type of film is capable of capturing, and what effect that has on how one approaches determining exposure (meter type and method). Slide films, for example, are more limited than negative films, and color varies from B&W. My suggestion is to pick whatever film type you work with most, and gain experience in using it.