I have been using a double layer of Rosco R-27 gel as a safelight filter and it has done well for me. I'm currently using two of those red LEDs, but I have older safelights to fall back on. It is possible to use some of the single spectrum LED lights that are new to the market for safelight use, but because they aren't tested or marketed for that purpose, you end up doing the testing yourself. Regular "red" bulbs aren't necessarily sources of sufficiently narrow spectrum red light, so they cannot be relied upon without testing. Other manufacturers make safelights to the OC standard. Most of them are also insensitive to the red light emitted by safelights designed for orthochromatic materials, but again it is very important to test. The newer (and now more common) materials that are designed for an OC safelight have a narrow band of insensitivity that matches the light output from that safelight. Our eyes tend to be more sensitive to the light from a Kodak amber (OC) safelight, so we would like to be able to use those safelights (the darkroom seems much brighter), but as most orthochromatic materials were not designed for use with an OC safelight, one needs to test whether they are compatible. You would use a red safelight with them, but that isn't ideal, because our eyes aren't particularly sensitive to red. Older orthochromatic materials were sensitive to blue light mainly, with some lower sensitivity to green.
Panchromatic means sensitive to all visible light. Only the now discontinued Panalure was panchromatic, and that was designed for making black and white prints from colour negatives. I'm afraid I have to differ a bit with Ian.Īs far as I am aware, no regular black and white paper is panchromatic. In general, panchromatic papers are not safe under red filters and simple red bulbs generally dont have the accurate filtering properties of a safelight and a Kodak OC filter. There are still a few orthochromatic papers from Europe, such as Foma that require a dim red safelight filter. Just about all printing papers are now panchromatic and should be used under a relatively weak OC-filtered safelight. Black-and-white panchromatic films are too sensitive to use under any safelight in most cases. The Kodak OC filter is the correct filter to use with panchromatic black-and-white papers. Panchromatic papers are somewhat insensitive to the amber-colored light passed by a Kodak OC safelight filter. These modern materials sensitive to all colors are called panchromatic. Later, films and papers were made sensitive to all, or nearly all, colors of light. Consequently, these materials could be used in a darkroom with dim red safelights provided that the exposure was limited in both time and intensity. That meant that they were partially blind to red light. Originally, all photographic papers and films were orthochromatic.
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