GB1438162A - Photographic exposure control system - Google Patents

Abstract

1438162 Photographic exposure control DAINIPPON SCREEN SEIZO KK 19 June 1973 [25 Aug 1972] 29136/73 Heading G2A An exposure control circuit subtracts the density range of an original from the density ranges reproducible with different filters to determine the filter to be used during photographing the original through a magenta contact screen to produce a half tone positive. As shown, the density ranges reproducible with a magenta filter, no filter (i.e. white exposure) and yellow filter are set in at 22, 23 and 24; the max. and min. densities of the original are set in at 28 and 29; the results A, B, C of the subtractions are sequentially fed to a comparator 33 which emits a signal wherever it receives a positive input; and the signals are fed to flip-flops 34 ab, 35 ab, 36 ab connected to AND gates 40-43. An output from gate 42 initiates white and yellow exposures, output from 43 initiates white and magenta exposures and an output from 40 or 41 prevents exposure, indicating that the density range of the original is below or above the reproducible range.