purposes. Black and white film can be developed in such a way as to compensate for extreme dynamic range, which of course makes it very useful for night photography. When exposure and development are precisely coordinated, black and white film can accommodate about 13 or 14 stops of exposure latitude, similar to the very best DSLRs. r e c i p r o c i t y Fa i L u r e All film suffers from reciprocity failure to some degree, meaning that the longer it is exposed, the less sensitive it becomes. Reciprocity failure is the breakdown of the constant relationship between light intensity and light duration on film. Under normal exposure conditions, a one-stop increase or decrease in the intensity of light reaching the film (controlled by opening or closing the aperture) can be compensated for by a one-stop adjustment in the duration of the exposure (the BLACK AND WHITE FILM RECIPROCITY COMPENSATION FOR LONG EXPOSURES Actual exposure Actual exposure Actual exposure