As numerous recent conversations have made clear, a big darkroom concern is stray light. I concur. My dye transfer printing required me to deal with errant photons at a level that no sane process would require.
As I've made clear, I prefer black darkrooms, equipped with lots and lots of lights. You may prefer differently. Talking about what color one's darkroom walls should be, one of the commenters in a previous thread remarked that "Dave is right Ctein is wrong." Nope. Dave's right for Dave, and I'm right for me. That's all you can say. The color you paint your darkroom is as much about ergonomics as anything, and that often boils down to what's personally comfortable. For example, I could live with a grey darkroom rather than a black one, but I could never deal with one painted a bright color. It would totally mess up my color vision.
This is not just an issue for me as a color printer, it comes up when I do black-and-white work. If you're the kind of black-and-white printer who is sensitive to the tone (as in hue) of your black-and-white prints, it could very well mess up yours. Color constancy in human vision is something that is easy to upset and it can take hours to equilibrate, especially along the yellow-blue axis. I can't imagine working in a brightly colored darkroom trying to judge how warm-or cold-toned a print paper is, and whether I want to tone the processed print, and by how much. Neutral surroundings, please! Doesn't matter if they're black, white, charcoal gray, or middle gray. I just really, really want something that won't contaminate my color vision.
Be that as it may, this column's really about telling you how to find the stray light in your darkroom, not what color to paint the walls.
Step one. Turn off the lights. Sit down. Close your eyes. Meditate on how wonderful your life is for at least five minutes. Open your eyes. Do you see any light leaks? Plug them! If it's a few twinkles around window frames or joints in the wall or between the wall and the ceiling, black electricians tape works wonderfully. If it's light that's leaking around the frame of the door, put some weather stripping or flaps around the frame to baffle it. Make all that outside light go away.
Step two. Put a negative in your negative carrier, put the carrier in the enlarger, and set up the enlarger as if you were making a normal-sized print. Leaving the lens cap on the enlarger lens, turn on the enlarger and turn off the all the room lights. Once more, sit there, eyes closed, in the semi-dark and contemplate your good fortune. After five minutes open your eyes and look around the room.
Look at the light leaks from the enlarger and see where they go. Trace any patches of light on the walls light back to their sources on the enlarger head. You might have to get ingenious at blocking them. Sometimes black tape works, sometimes you'll have to build little baffles and hoods out of plastic, paper, cardboard, and tape; just do whatever it takes to trap the leakage from the enlarger. Be careful, though, not to close off ventilation ports that let cooling air into the larger head.
Pay extra special attention to any light that might be leaking down in the direction of the easel. You won't be able to get rid of all the stray light, but you'll be able to get rid of a lot of it. You'll likely have to repeat this step several times, making your modifications and checking your work, since doing the work in the dark may be difficult or even unsafe.
Test your success so far by taking a sheet of plain white paper, drawing a big fat black X on it with a wide felt tip marker, and putting the sheet of paper in your paper easel. Prepare the enlarger (and yourself) the same way you did in step two. After the obligatory contemplative five minutes, look at the paper easel. Can you see the X? You shouldn't! Or, at least, it should be nearly invisible—there should be that little light reaching your print easel.
Step three. Find a negative that has some area that is truly maximally dense. Perhaps a photograph you made where the sun is in the field of view? Doesn't matter what, so long as there's an area that is as close to D-max as possible. Got it? Put the negative in a carrier. Now, drop a bit of something totally opaque on top of the negative overlapping the D-max region. It can be a chip of cardboard, a hair, a bit of wire, anything that will make an absolutely black, sharp-edged shadow within the D-max area.
Put the negative carrier in your enlarger and focus the image sharply. Stop the lens down two or three stops to minimize flare and maximize contrast. Take a close look at the D-max area of the negative projected onto the print easel. Is the shadow of the opaque object within that area clearly much darker then the D-max of the film? If so, you're good!
If not, you'll need to figure out if it's flare or stray light within the enlarger system or light reflected off the print paper and scattered back again. A helpful diagnostic is to substantially reduce the magnification of the projected image. If you normally print 8x10, shrink the image down to 4x5 by lowering the enlarger head. That makes the projected image 3–4 times brighter, but it doesn't increase the amount of backscattered light. If the opaque shadow becomes much darker relative to the negative when you do this, then it's most likely backscatter that's causing your problem. You'll need to track that down.
If the relative clarity (or lack thereof) of the shadow in the projected image stays the same, then any problems you're having separating out tones of these dense areas are due to flare or light scattering within the enlarger head and/or the enlarger lens. You'll have to figure out what to do about that, but at least you'll know the problem isn't your darkroom.
Ctein's regular weekly column appears every Thursday morning, for some value of "morning." (Note time stamp on this week's column!)
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Original contents copyright 2010 by Michael C. Johnston and/or the bylined author. All Rights Reserved.