safelight

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An amber (light brown) safelight for use with certain black and white photographic papers.

Safelight is a light source suitable for use in a photographic darkroom. It provides illumination without the wavelengths of the light spectrum to which the material in use is sensitive. A safelight usually consists of an ordinary lightbulb in a housing with a coloured filter. It is possible to buy special bulbs and fluorescent tubes which are coated with a filter directly on the glass. Low-pressure sodium vapor lamps are also commonly used in larger darkrooms. They emit nearly monochromatic light at 589nm, to which photographic materials are insensitive; as a result they can be extremely bright while still "safe".^{[citation needed]}

The word ‘safe’ in ‘safelight’ is relative as in most cases a sensitised material will eventually be affected by its safelight if it is exposed to it for an extended time period, and there are many photographic materials that need handling in total darkness. ^[1]

Differently-sensitised materials require different safelights. orthochromatic materials, such as lithography films and lith papers are sensitive to yellow light, and thus require a red safelight; modern photographic papers have only blue and green sensitivity, and can be handled under yellow safelights.^[2]

Exceptions to this are panchromatic papers such as Kodak Panalure, which must be handled under an amber safelight filter, or in complete darkness.^[3]

References

1. ^ http://www.kopecny.net/download/ilford/ilford_safelight.pdf
2. ^ Langford, Michael (2000), Basic Photography (Seventh Edition), Oxford: Focal Press, pp. 237, ISBN 0 240 51592 7 
3. ^ Kodak Professional Panalure Select RC Paper, Rochester, New York, U.S.A.: Eastman Kodak Company, June 2005, pp. 1, http://www.kodak.com/global/en/professional/support/techPubs/g27/g27.jhtml 

See also

• Purkinje effect

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