Method and apparatus for print exposure control

Details Method and apparatus for print exposure control Method and apparatus for print exposure control

1976-09-10

1978-07-18

Hix, L. T.

Photocopying

Projection printing and copying cameras

Multicolor picture

355 38, 355 77, 356175, 356203, G03B 2776, G03B 2778

Patent

active

041012160

ABSTRACT:
A method of controlling the exposure in the production of photographic color prints by scanning an original line-by-line and point-by-point with three primary colors to determine the density of each primary color at each point. At each scanned point the difference between the density values of a pair of two of the three primary colors and the difference between another different pair of the three primary colors are compared with the corresponding density difference values of a reference original having a constant density distribution comprising the three primary colors. The density difference comparison forms a selection criteria to determine whether each point scanned is to be used to form density values from which the exposure values for the three primary colors are formed to control exposure of the print material. The selection criteria is as follows: ##EQU1## WHERE D.sub.i, D.sub.j and D.sub.k denote the densities of the scanned points for the primary colors i, j and k; a, b and c are constant factors; d.sub.1, d.sub.2 and d.sub.3 are constant density values and D.sub.N.sbsb.i, D.sub.N.sbsb.j and D.sub.N.sbsb.k denote the densities for the primary colors i, j, and k of a reference original; the scanned points which do not satisfy these conditions being disregarded in determining the area densities.

REFERENCES:
patent: 3455632 (1969-07-01), Neale et al.
patent: 3888580 (1975-06-01), Amano et al.
patent: 3937573 (1976-02-01), Rising

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