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Luminance nonuniformity is present in both hardcopy and softcopy images. A light box with fluorescent lamps has hot spots directly over the lamps when measured with a meter. These are visible as shown in Fig. 6.1. Light is reflected off the interior surfaces to be summed with the photons that exit directly into the platen (diffusing plate). A light box has internal corners and edges in which the ability to maintain uniformity is compromised. For a quality light box, this can be as much as 30% from center to edge. A poorly maintained one can be as high as 50%. The question is whether the nonuniformity can be observed when reading film. It turns out this is difficult to discern and therefore is a minor inconvenience.
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