Journal of the Society of Motion Picture and Television Engineers (1950-1954)

these colors reflected from the original subject. These colors expose the camera film, forming the negative image in cyan, magenta and yellow dye, respectively. From the color negative three separation positives are prepared on Eastman Separation Panchromatic Safety Film. These positives are exposed through red, green and blue filters, giving a permanent silver record of each of the three dye images. It is now possible to print these records in the correct dyes of the internegative film. This is shown in the lower portion of the diagram where the sensitivities appear on the left, the dyes formed on the right. Since it is necessary that the record of the dye images of the negative become finally the corresponding dye images of the internegative, it is obvious from the figure that the red-separation positive must be printed with green light. Similarly, the magenta dye in the bluesensitive layer requires the green separation positive to be printed with blue light, and the third, or blue, separation must be printed with red light. Thus, the original dye images of the negative will appear in the same dyes in the internegative and will give a print with normal color reproduction. In order to achieve proper tone reproduction in printing the color internegative from the three separation positives, it is necessary to adjust the exposure so that the straight-line portion of the sensitometric curve of the color internegative is used. Underexposure at this stage causes loss of contrast in the shadows, as observed in the final print. Overexposure produces an internegative that may be too dense to print and may lead to low contrast in the highlight areas. The last stage in Fig. 5 shows the printing of the internegative on Eastman Color Print Film. This stage of printing may be done with white light modified as may be found necessary by Kodak Color Compensating Filters, or single or multiple light-source printers may be employed in which red, green and blue light are appropriately mixed at the printing aperture. We may turn now to a more specific study of these operations and to the precautions which must be observed. Because of the presence of the dye masks in the original negative, the choice of filters in making the separations is critical. The set of filters recommended for making these separations is: Separation Positive Red Green Blue Kodak Wratten Filter No. 70 16 + 61 48A + 2B These filters have been chosen to give the highest contrast and the most satisfactory color separation from the maskeddye negative images. There are fewer restrictions on the choice of filters to be used when printing the separation positives on the internegative. Because the printing at this stage is from silver images, no effect is produced on the contrast or color reproduction by changing the transmissions of the filters unless the transmissions are made so broad that the filters transmit in an adjoining region of the spectrum. For example, the total transmission of the green filter must not be so broad that it exposes either the red or blue-sensitive layer of the internegative film. The recommended filters have been chosen in this case to match the peak sensitivities of the internegative film as follows: Yellow printer or blue separation Magenta printer or green separation Cyan printer or red separation Kodak Wratten Filter No. 29 34 + 38A 16 -f 61 222 March 1953 Journal of the SMPTE Vol. 60