Shedding New Light on Darkroom Illumination
Despite their popularity, absorption filter safelights have some real disadvantages. In addition to the less than ideal spectral output, they are subject to fading, mostly from the heat of the incandescent bulb. Kodak's recommendation to test the effectiveness of the filter at regular intervals is largely ignored, judging from the many "un-safelights" I have seen with cracked or faded filters. Continuous use may require filter replacement several times a year, at relatively high cost for filters and maintenance.
These safelights are also subject to tampering by workers seeking brighter light, usually by increasing bulb wattage, or deliberately cracking or fading the filter. The glass filters are also difficult to cut into custom sizes or shapes, for example, to use in flashlights.
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