American cinematographer (Sept 1937)

360 American Cinematographer • September, 1937 TWO NEW FILMS FOR DUPLICATING WORK Paper Presented at Spring 1937 Meeting of Society of Motion Picture Engineers by Messrs. C. E. Ives and J. I. Crab- tree of Eastman Kodak, Rochester, N. Y. (I) INTRODUCTION I T HAS long been recognized that duplicate negatives of sufficiently improved characteristics would be of value in protection against loss through damage to the original nega- tive. Capstaff and Seymour 1 in an earlier publication have defined a per- fect duplicate negative as one which would give prints identical in every respect to those obtainable from the original negative. Since that time two papers have been published 2 3 giving the results of later work on photographic materials for duplicat- ing work and methods for their use. Recent progress in the photo- graphic emulsion field has made avail- able new duplicating positive and negative films which possess in a high degree the characteristics most needed for making satisfactory dupli- cates, and excellent results from the standpoint of quality and graininess have been obtained through their use. (II) THE DUPLICATING POSITIVE FILM The Duplicating Positive (emulsion series 1365) consists of a yellow dyed positive emulsion of medium contrast coated on a clear base. As shown in the curves in Fig. 1 suitable emulsion quality and de- velopment characteristics are ob- tained with the D-76 type of de- veloper in the working gamma range of 1.0-1.5. There is practically no fog under normal conditions of use. It will be noted from the exposure scale that exposures somewhat greater than usual have been employed. The East- man 116 sensitometer gives proper ex- posures for process control purposes Fig. 1 (a). Exposure curves of Duplicating Positive (Emulsion 1365), with D-76 developer. with multiple exposures of three to eight times. The sufficiency of exposure under any particular condition can be judged from the extent of the straight-line portion of the curve obtained. It is usually found that a triple exposure is sufficient when the 116 sensitometer is set for the positive exposure con- dition with the exception that the light-filter is removed. The color- sensitivity of the Duplicating Positive emulsion is similar to that of Motion Picture Positive (series 1301) and, therefore, this film can be handled under the positive room illumination furnished by the Series 0 Wratten safelight in an indirect fixture. (Ill) THE DUPLICATING NEGATIVE FILM The Duplicating Negative Film (emulsion series 1203) consists of a low-contrast panchromatic emulsion coated on a gray base of the same type as used for other negative film. The curves in Fig. 2 (see Pages 000 and 000) show that with the D-76 type of developer proper emul- sion quality and control of contrast are obtained in the recommended gamma range of 0.6 to 0.7. Emulsion 1203 is exposed sufficiently when a single exposure is given with the lift sensitometer at the normal positive setting. The distribution of spectral sensi- tivity is shown by the spectrogram in Fig. 3, the indications of which will be found useful for comparison with those of other emulsions, as shown on page 64 of the handbook of “Mo- tion Picture Laboratory Practice.” 1 This extended color-sensitivity gives the Duplicating Negative emulsion additional speed which is of consider- able advantage where optical print- ing is employed, and particularly in the case where a master positive is dense. While the panchromatic emulsion is sensitive to all portions of the visible spectrum, the green Wratten Series 3 safelight has the advantage of visual efficiency at the level of illu- mination employed in photographic