IN order to measure precisely the absorption of light by toned and tinted motion picture film, a special instrument was designed and constructeld.
The optical system of this instrument is so arranged that the transmission value measured is that of the effective transmission of the picture as projected in the standard motion picture1 machine.
Since such a picture is composed of silver deposits which are diffuse in nature, that is, light scattering, they must, in order to obtain the value of effective projection transmission, be illuminated under precisely the same conditions as exist in the projecting machine.
Furthermore, since in dealing with toned and tinted film, color differences are involved, it was necessary to use a flicker method for measuring the desired values of transmission.
The apparatus constructed for this work is therefore called an " integrating flicker photometer," and measureis the mean effective projection transmission of the sample under consideration.
The results obtained in the case of tinted pictures show that the tinting process producels no change in the physical contrast of the picture b'ut merely decreases the transmission.
The transmission values for the series of colors examined varied from 26 per cent. in the case of tine violet to 82 per cent. in the case of tine yellow. The results obtained with the dye tone samples shorn that the decrease in transmission is not directly proportional to the density of the deposit, but that the deposits of higher density are more affected by the trelatment than the very low densities. This tends to produce a slight increase in the physical contrast of the picture.
The selective action, however, is confined largely to the densities lying on the toe of the curve, which results in a lengthening of the straight line portion of the curve' without materially changing the slope of the straight line portion.
The transmission values for a series of dye toned samples vary from 43 per cent. for the safranine to 89 per cent. for one of the auramine tones. These values are relative to the transmission of the untoned sample. In the chemical toned samples, the selective intensification is much g Communication No. 122 from the Research Laboratory of the Eastman Kodak Company and published in Trans. SOC. Mot. Pit. Eng., No. 12, p. 85.