| Incorrect safelighting can degrade every print you make, though the effect is greater the longer the paper is exposed. A simple check can tell you if your safelight is ok.
Heres How:
1. You need a darkroom with photographic safelighting, and processing facilities for the paper (or workroom film) for which you want to check if the light is safe.
2. Turn out the room light and turn on the safelight.
3. Cut a piece of paper or film at least 3 inches by 1 inch.
4. Put your enlarger head near the top of the column and close the lens to f16.
5. Cover over the lower half of this strip by placing an opaque object on it. Make a test strip on the upper half using succesive exposures of 4 seconds to a total of 20 seconds.
6. Process the test strip and examine it.
7. Choose the shortest time to produce any tone, and expose a new strip using this.
8. Put a coin on the exposed paper and leave it for the typical time a piece of paper might be exposed to the safelight before the start of development - perhaps 1 minute.
9. Process and inspect this sheet. There should be no visible image of the coin.
10. If you can see an image of the coin, then turn the safelight down or move it further away. and try again.
11. If a further test still gives a visible image you may need to try a different colour safelight - read the paper manufacturers instructions.
Tips:
- Variable contrast papers in particular often cuase problems in black and white darkrooms, as they often use emulsions with much more green sensitivity than traditional printing papers.
- Lith and line films are normally made for use with a red or deep red safelight rather than the yellow or orange lights normally found in black and white darkrooms.
- Colour papers are sensitive to all colours of light. The best safelights for them are sodium or LED with a very narrow range of wavelengths, but even with these you need to take care.
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