Exposure control for photo printer - uses series of even amplitude flashes and control counter

摘要

The film copying equipment uses electronic flash exposure for an accurate control, with a series of flashes of even amplitude to reach the required exposure. The number of flashes is monitored by a programmed counter. The selected exposure is fed to a control counter and the actual flashes are counted on a second counter. A comparator circuit terminates the flashes when the counts are equal. For colour printing three pairs of counters are used.