Optics: measuring and testing – Refraction testing – Prism engaging specimen
Patent
1975-03-04
1976-04-27
Corbin, John K.
Optics: measuring and testing
Refraction testing
Prism engaging specimen
96 23, 96 24, G01J 346
Patent
active
039531350
ABSTRACT:
A method of approximating the characteristic curves of a color film exposed at a variety of color temperatures is provided.
The method involves the use of a linear curve which relates the .DELTA. log E change of blue and green exposure with change of color temperature. This linear curve is derived experimentally from the characteristic curves obtained by exposing several color negative films to a sensitometer, including a step tablet and a means for varying color temperatures. The films are exposed at color temperatures ranging from 2900.degree.K to 6700.degree.K and then processed in a color developer. Transmission densities of the developed film to red, green, and blue light are determined with a densitometer and the results plotted as a curve relating red, blue, and green density to relative log exposure. These characteristic curves are then analyzed by placing them over the curves obtained at 6700.degree.K so that the red curves are superimposed. The change in blue and green exposure with color temperature for each set of curves is determined graphically along each curve. The .DELTA. log E determinations are averaged and the results plotted as a linear curve relating the .DELTA. log E change of blue and green exposure from 6700.degree.K to 2900.degree.K. This curve can be plotted as .DELTA. log E vs. color temperature or Mired Value, which is a value equal to 1,000,000/color temperature. This linear curve can then be used to determine the characteristic curve of an unknown color film exposed to any color temperature providing the characteristic curve for one color temperature is determined experimentally. This is done by determining from the linear curve the .DELTA. log E change for the blue exposure and the green exposure from the experimental color temperature to the new color temperature. The change is plotted on the characteristic curve of the known temperature to produce the predicted points for the unknown curves.
REFERENCES:
L. P. Clerc's Photography Theory and Practice, Vol. 3 Films, edited by D. Spencer, N.Y., Am. Photo, 1970, pp. 372-384.
Levy Marilyn
Schwartz Milan
Corbin John K.
Edelberg Nathan
Evans F. L.
Gibson Robert P.
Gordon Roy E.
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