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Adding and Subtracting Contrast?

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Hi, my name is Jaz, and I am new to the black and white film printing process. I haven't had much experience with manipulating contrast and I want to understand thoroughly how to use it as a tool to enhance my photos. I am wondering how to determine the appropriate time to add or lessen contrast. What do I analyze and look for in a print to know I should add magenta or yellow? All responses are greatly appreciated. Edited by jazlynquish
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A good resource is Kodak's "Black & White Darkroom Dataguide", or their "Creative Darkroom Techniques", or even Ansel Adam's "The Print". There are a variety of techniques to answer your question, starting with how the film itself was exposed and developed, and ending up with the types of paper used in printing, the exposure and development techniques, and the filters used. You could just experiment around, which is probably a good way to learn, but expensive. Best to get some solid education on the processes in first, before deciding how to best experiment...it will save you money and frustration in the long run.
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It is called "black & white" because those two extremes should be somewhere visible in your final print. If your print looks grey & grey, it lacks contrast. If too huge areas of your print turn out balck and white it might be time to reduce contrast. Use test stripes, not entire sheets of paper. -Place them into the darkest and lightest part or if you are shooting people to see their eyes printed.

Maybe a local library has some book on darkroom stuff?

A warning: Until you are really experienced better always do another round of test stripes when you determined to change your contrast. - If you are going for more correct exposure becomes harder to hit. If you are going for less something might suddenly look wrong. Also your color head's filters will alter exposure time / need compensation.

Some negatives don't lend themselves to straight printing at any contrast. - Maybe you can master them with dodging & burning technique but that takes a while to get lerned.

Take notes how you did stuff.

Edited by Jochen
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One approach to controlling contrast at the printing stage is to first nail the print exposure for the highlights (a subjects white T shirt or the sun lite side of a face). Only then look closely at the shadows or dark tones in the print. If the dark tones look too gray - add contrast. If the dark tones are so dark they obscure details you can see in the negative - reduce contrast. If you find you are having to, more often than not, add contrast - reduce your negative development time and vise versa.
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If you find you are having to, more often than not, add contrast - reduce your negative development time and vise versa.


Underdevelopment (reduction of development time) gives less contrast on the film requiring the use of higher contrast paper. Conversely, increased development results in more contrast on the film requiring a lower contrast grade of paper when printing.


Film can accommodate about 1000:1 contrast ratio between the darkest shadow and brightest highlight. Black and white paper will have a contrast ratio of 100:1 - 10x less than film.


This means to have detail in the highlights and detail in the shadows you must have a subject with a contrast ratio that does not exceed 100:1 or you compensate for the subject's contrast ratio by altering the film development.


In Zone System terms, a low contrast subject would require "expansion" or increased development time, while a high contrast subject would require "contraction" or a reduction in development time. A subject with a tonal range of 9 zones would require a -1.5 to -2 development to move the highlights from Zone 9 down to Zone 7 to 7.5 (depending upon your enlarger, print developer, etc.).


Conversely, a low contrast subject with a 5 zone tonal range would require a +2 to +2.5 expansion (over development) to move the highlights from Zone V to Zone 7 or Zone 7.5.


In simple terms - you expose for the shadows and develop for the highlights.


Unfortunately, that approach only works using sheet film or where you expose an entire roll on a single subject. If you have multiple subjects on a roll of film, then you have to make a decision to sacrifice all of the exposures for one or two that you feel are best, or develop the film for an average exposure, and then make whatever contrast changes are needed through printing - including dodging and burning.

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  • 2 weeks later...

As above, a print with too little (gray and gray) or too much (no gray, just black and white) usually doesn't look right.


But you can compress the scene somewhat, maybe a 300:1 scene range into 100:1 paper, which isn't so bad.


Also, often enough there isn't much interesting in the darkest and lightest parts of an image, so you can let those go to complete black and complete white.


Mostly, you have to make some prints, look at them, and see if you like them. Also, show them to other people and see what they say about them.

-- glen

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