Although black-and-white papers are vulnerable to daylight until "fixed," a certain amount of "safe" light is allowed in the darkroom. It is this amber, red or green light (contingent on the sensitivity of the particular enlarging paper you’re using) that allows us to find our way around while we prepare to print. We can find things in the darkroom, take paper out of boxes, trim paper on a paper cutter, align printing paper on an easel, place negatives in carriers, answer the phone or turn the dial on a radio.
Safelights are only for use when printing black-and-white. Color printing requires total darkness, which means you must have everything in place before beginning the printmaking process. If your smartphone lights up when somebody calls, put it away or turn it off.
A typical safelight is generally positioned at least three feet from the enlarging easel. Some safelights can be rotated so the light faces up or down, and others feature louvered doors that can be opened or closed to regulate light intensity. Even though the safelight can be plugged into an AC outlet, many printers prefer to plug it directly into the timer, whose circuitry will likely be built to control the safelight. When the timer is turned on, the safelight automatically shuts off. When the exposure time is completed, it automatically comes back on. Like easels, there are many types and sizes. Depending on the size of your darkroom, it is possible to use more than one safelight, as long as they are spaced sufficiently to prevent paper from fogging. Ideally, safelights should be tested to make sure they do not fog the paper. A simple test to determine if your safelights are too bright is to place a piece of unexposed enlarging paper on your easel, place a few coins on it for about five minutes, and run the paper through the developing solutions. If you can make out the shapes of the coins when the lights come back on you should redirect or reposition your safelights and repeat the process until you can no longer detect the reverse outlines of the coins.
|KODAK Safelight Filter||Color||Use|
|OA||Greenish yellow||Black-and-white contact and duplicating materials, projection films|
|OC||Light amber||Contact and enlarging papers|
|OO||Light yellow||Flashing halftones made through a KODAK Contact Screen for contrast control|
|1||Red||Blue-sensitive materials and most phototypesetting materials|
|1A||Light red||Slow orthochromatic materials|
|2||Dark red||Fast orthochromatic materials, green-sensitive x-ray films|
|3||Dark green||Some panchromatic materials|
|6B||Brown||Blue-sensitive x-ray films|
|7B||Green||Some panchromatic materials|
|8||Dark yellow||Color print and color intermediate motion-picture films|
|10||Dark amber||Color negative papers, materials, panchromatic black-and-white papers|
|11||Appears opaque, transmits infrared radiation||For use with infrared inspection devices|
|13||Amber||Color negative papers, panchromatic black-and-white papers|
|GBX-2||Dark red||Most blue-sensitive x-ray films, most green-sensitive medical x-ray films|