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CINEMATOGRAPHIC ANNUAL
to visual density will depend upon the spectral selectivity of the photographic deposit, and this ratio will combine with the specularity of the printing light to yield a printing coefficient for the negative which includes the color coefficient as ordinarily understood and the geometry of the printing operation. The printing coefficient may be equal to, less than, or greater than unity.*
Filters introduced in printing the sound negative alter the quality of light falling on the negative. This may affect the negative printing coefficient at the same time that the color change affects the gamma to which the positive is developed. The two effects may be opposed: one case was found where they cancelled each other, and the filter served merely to reduce the light as would a neutral gray.
Replacing the 60-watt tungsten lamp by a 200-watt, gas-filled lamp and suitable filter has been tried by one laboratory in Hollywood. The effect was a 12 per cent reduction in over-all gamma in addition to a reduction in exposure.
i2
08
0.4
H & D CURVE T = 0.50 E.K. POSITIVE CINE FILM
DAYLIGHT TIME SCALE C MACHINE DEVELOPED )
-08
-0.4 00 LOG. NEG. EXP :
0.4 Ofl 1.2
METER -CANDLE SECONDS
1.6
Fig. 1 . Sound negative development.
Sensitometric Results
The accompanying figures will illustrate the foregoing. Fig. 1 is an H & D curve on Eastman positive emulsion, obtained with the Eastman time scale sensitometer, and developed in a sound negative bath to a gamma of 0.50. Visual diffuse densities are plotted against log meter-candle-seconds. The same development would be expected to give a gamma of 0.53 for light-valve exposures, where visual diffuse densities would be plotted against log valve spacings. A slightly shorter development would give a light-valve gamma of 0.50 and, as stated above, the resulting curve would register with the curve of Fig. 1.
For determination of color coefficient see reference No. 3.