Filter pack correction method in color photography

Details Filter pack correction method in color photography Filter pack correction method in color photography

1975-03-04

1979-03-27

Brown, J. Travis

Gas separation: apparatus

Magnetic separating means

Electromagnet

96 23, G03C 700, G03C 716

Patent

active

041463943

ABSTRACT:
A method of predicting the filter pack correction required to print a color ilm that has been exposed at any illuminant color temperature is provided without the need for a grey card in the scene.
This method involves first the experimental determination of the correction filter pack required to produce a grey print from any of the following: the clear unexposed portion of the negative, an image of a continuous wedge or step tablet exposed at a known color temperature on a sensitometer, or the image of a grey card on a roll of film that was exposed at a known color temperature. The red, blue, and green densities of the grey card, or a particular exposure on the characteristic curve, are added to the densities of the correction filter pack to obtain a value called the Total Negative Grey. In the case of the clear portion of the negative, a correction factor of 0.02 green and 0.13 blue must be added to the base fog densities before the densities of the filter pack are added. The densities produced by the image of a grey card in a scene exposed at a different color temperature are then simulated from a simulated characteristic curve. These densities are then subtracted from the Total Negative Grey to obtain the filter pack required to print the scene exposed at a new color temperature.

REFERENCES:
focal Encyclopedia of Photography .COPYRGT.1972, pp. 322-323.

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