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Darkroom technique used to darken selected areas of a print. Several image-editing programs also include a similar tool to darken pixels.
Indicates the energy content of the storage capacitors in an electronic flash. One Joule is the light output given by one watt burning for a second. Therefore a flash unit with a storage capacity of 300 Joules can supply the power to light a 300W lamp for one second. It doesn't take into account any electrical loss between the flash capacitor or flash tube, or the efficiency of tube and reflector.