Radiography in Modern Industry - Kodak

loading-bench activities are carried on. Only one level of illumination is usually provided in aprocessing room for automatic processing, since the manipulation of unprocessed film is reducedto a minimum.The "safeness" of processing room illumination depends equally on the use of the propersafelight filter, the use of the proper wattage of bulb, the proper placement of lamps with respectto film, and not exceeding the maximum "safe" time of exposure of the film to safelightillumination.Exposed films are more sensitive to fogging from the safelight illumination than are unexposedfilms. Hence, it is especially important to guard the exposed films against prolonged exposure tosafelight illumination. Note that the screen-type films are more sensitive to fogging by safelightillumination than direct-exposure films.A simple method of checking the safelight of illumination is to test it with the fastest film used inthe laboratory, as follows: An exposure is made of a stepped wedge. In the processing room, theholder is unloaded and the film placed in the area where it is normally handled. Part of the film iscovered with opaque paper. The remainder is exposed to the safelight illumination for themaximum time normally needed for handling. The test film is then given standard processing. Ifno density shows on the uncovered part that received the safelight exposure, as compared withthe covered part, the lighting may be assumed to be safe.Radiography in Modern Industry 133