Do you want a precise definition of contrast, or a procedure for deciding what grade to print at?
Defining contrast well is an interesting subject, and part of it is addressed in this thread. In that thread, I had a better idea, and @Stephen Benskin explained some things and provided some reference material showing that my better idea was a worse idea. But a crucial concept through that thread is that of "exposure range", which is the amount of exposure needed to go from a specific low density to a specific high density. This applies to both negatives and prints, and the two exposure ranges should somewhat match. It's called LER because it's the log of exposure range.
Given a negative, a common procedure in the darkroom is:
- Guess the grade, and make a test-strip to obtain correct exposure for the highlights.
- Change grade so that shadows appear as you want them (more test strips).
With my definition, you can have an image with both high contrast and "mainly just mid tones".
And just randomly guessing at grade is really killing the paper budget, even just using the cheapest 5x7 it is getting expensive.
i HAVE thought one of those density meters would be nice to try but i just dont want to drop that much cash on something without KNOWING it will do what i need.
Money and electronics won't buy you good prints. The idea behind that approach is to determine exposure and contrast such that spot "X" of the negative will print just maximum black (or 90% of Dmax, or whatever), and, likewise, that spot "Y of the negative will print just shy of pure white (or D=0.1, or whatever). (even to match mid-tones with a reflection gray scale...) That approach fails for the following reasons:i HAVE thought one of those density meters would be nice to try but i just dont want to drop that much cash on something without KNOWING it will do what i need.
Look, it's either going to be a theory-based approach where you substitute the trial-and-error of using test strips/prints (to an extent) with measurements and theory, or it's going to be the manual labor of trial & error and the consumables expenses that go with it.
Use a controller that works with an easel meter.
Guess the grade, and make a test-strip to obtain correct exposure for the highlights.
- Change grade so that shadows appear as you want them (more test strips).
Money and electronics won't buy you good prints. The idea behind that approach is to determine exposure and contrast such that spot "X" of the negative will print just maximum black (or 90% of Dmax, or whatever), and, likewise, that spot "Y of the negative will print just shy of pure white (or D=0.1, or whatever). (even to match mid-tones with a reflection gray scale...) That approach fails for the following reasons:
Wrapping up, and IMHO: an electronic device may help you determine a good approximation of the contrast and exposure, and to cut down on initial steps of trial and error. Experience and a good eye can achieve the same (not that I'm there yet). Then dedicated test strips in critical regions of highlights, mid-tones, and shadows. Then a full-frame test print, that will reveal global relations between the tones, that the test strips could not. Then...
- How do you choose spots "X" and "Y" on the negative? A specular reflection that subjectively is beyond white? a keyhole into a dark room that is subjectively beyond pitch black? Of course, I'm exaggerating, but that is to convey the idea.
- How to choose the reproduction tones "or whatever" in the above? For light tones, as you push towards paper white there comes a point where you actually lose brilliance, because the tone reproduction curve rolls over at the shoulder; wehn is "just right"? And some shadow tones (in some images) can be safely dropped into maximum black.
- The reproduction of mid-tones plays an important part in the feeling conveyed by a print, IMO as much as the placement of the highlights and shadows.
A contact sheet may also be useful, not just to select "interesting" frames, but to transfer exposure (grade-fstop-time) information, gained through hard work from one fame to another. Hhmmm frame 3 prints lighter than frame 2 on the contact sheet, so I'll need to expose longer (other things equal...); ditto for paper grade.
"DON'T read books. Make the prints and look at them w/ your own two eyes. You'll quickly understand this, it's truly a visual thing.
Think of it as cooking. You can read cookbooks until your eyeballs fall out, but the minute you put something on the stove and taste it, ah, then you know."
! Exactly
I would appreciate an image as an example of that
Picture a ray of light going through the negative, then through the center of the enlarging lens. You are standing in front of your enlarger. If the ray of light has crossed the back of the negative, as it goes down on its inclined path, it moves to the front. Same for left-right.And i have yet to find a book that can explain why the image is flipped by the enlarging lens.
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