How Dark is Dark Enough

R

richiedcruz

Guest
For the past month, I have been making my own contact sheet at home, then getting prints run up by my favorite lab. I have been mainly doing this at night, but I got tired of staying up late and decided to try to turn my bathroom into a proper temporary darkroom.

I got some black posterboard to black out the window and sealed up the door, but there are still innumerable light leaks that will not go away no matter how much tape I use, because of various vents that I cannot get to.

My question is how dark is dark enough? Can I just get away with doing everything really, really fast?

I am also going to make a run down to my local cloth store, because I realized that there were lots of pinhole leaks in the seal that I got, and taping up the door every time I want to run up a contact sheet is wasteful. Will any kind of black cloth do? Or should I bring a flashlight with me to check how opaque it is?

Thanks,

Richie
 
You're the only one in a position to answer the question. Try this: cut a small strip of printing paper. Place a coin on it. Let it sit for about two minutes. Develop the paper normally.

If you can see the coin's impression on the strip, the excess light is a problem.
 
Do the trick Alan spoke of above... except that I, personally, would leave the coin on the paper for about 15 minutes. But I was always anal about darkroom work and avoiding base fog on papers was one of my (many ;) ) obsessions.

Tom
 
a variation of the coin trick is to expose a piece of photo paper for various lenths of time to determine the exposure that results in a very light grey in the processed "print". Then repeat this exposure with a new piece of paper, then place a coin on it for 2 or 3 minutes, then process to see if you can see the effect of the coin on the light grey print. The purpose of this is to sensitize the paper to light to better approximate what really happens when you are printing. (I didn't explain the reasoning very well.)
 
FrankS said:
a variation of the coin trick is to expose a piece of photo paper for various lenths of time to determine the exposure that results in a very light grey in the processed "print". ...
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What Frank says is correct. There is a certain threshold of exposure to white light below which there will be no visible effect on the paper. However, the paper has still received some exposure - say 2 sec. at f16- and those 2 seconds of exposure do count. A further exposure of 1 sec will produce a visible tone, however, the total exposure time has actually been 3 seconds.

In effect, the paper has been "hyper-sensitized" by pre-exposure. In fact this trick was often used by press photographers in the sheet-film days, who would pre-flash their film to produce an increase of speed.

Since any fogging from light will effect the brightest tones in your print the most, it makes sense to pre-expose your test paper to the point that it represents those tones. This simulates the actual working conditions of print-making better than using an unexposed sheet. To quote Mr. Adams, "the slight exposure the whites of the print represent is reinforced by subsequent exposure to the safety light, and increased density may result".

So far as blacking out you dark room goes, I found that lining the door frames, and door sides with black masking tape cut out all the light leaking in from that source. A lot more convenient than black drapes covering the whole door, which is what I had before. Weather stripping on the bottom of the door finished the job.

As to the vents, which you'll want to keep open, you could make shields to cover them out of chloroplast (that plastic stuff that looks like corrugated cardboard), painted flat black on the inside, to block the light but still let the air through. With enough chloroplast, and a hot glue gun, you could probably build a whole house.
 
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Thanks for the advice everyone. DD and Frank, I think I understand what you are each saying, but let me run this by both of you. Do you mean that by figuring out how much the light that is leaking into my darkroom is pre-exposing the paper that I can then compensate for it by shortening my exposure times?

Thanks,
Richie
 
Nope! This test will tell you if you have too much light coming into your darkroom and having a negative affect on your prints, or not. If you can't see the "shadow" of the coin, then no problem as is. If you go through this proceedure and see the coin's shadow, that means you've got to light-proof your room better.
 
Frank,
Thanks for clearing that up for me. I am trying to get the hang of doing my own b & w printing and going through all the books that I have bought on the subject.

At least developing my own film has been easy :)

Richie
 
richiedcruz said:
Frank,
Thanks for clearing that up for me. I am trying to get the hang of doing my own b & w printing and going through all the books that I have bought on the subject.

At least developing my own film has been easy :)
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True, but printing is the fun part. :D

Admittedly, testing safety lights is a pain in the neck, but you only have to do it once, and then you know what the limits are. The fact is that so called safety lights really aren't totally safe. Given enough time, they'll all fog paper, so it's good to know how much time that takes to happen (in my dark room, it's over 10 min, I stopped testing at that point).

The great part about doing your own printing is that with a little care and attention, you can easily produce prints that are better than what you'd get from most custom labs, and you probably know how much those cost. That and you get to make your pictures look exactly like what you want them to look like.
 
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