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Panchromatic Negative Film — Jones & Crahtree 175
27, 28, and 29. From Fig. 29 it is seen that with fairly complete development (10 minutes) the contrast obtained with panchromatic film is slightly greater than with Super Speed film and slightly less than with Par Speed film. With the pyro developer in question 8 minutes development with panchromatic film will give the same contrast as 10 minutes development with Super Speed film. In general, panchromatic film requires slightly longer development than Par Speed film and slightly less than Superspeed film.
With Par Speed film gamma increases more rapidly with shorter development but the ultimate contrast obtainable is approximately equal in all cases.
An average negative on panchromatic film is usually developed to a gamma of 0.8. Referring to Fig. 28 this degree of contrast is obtained in 7 minutes with the MQ-80 formula, 13 minutes with pyro, and 18i minutes with glycin at 68°F with fresh developing solutions. The developer formulae and instructions for developing motion picture film by the reel and tank systems have been given in a previous communication.^
The curves at the bottom of each figure show the rate of growth of fog with time. For a fixed contrast pyro, glycin, or MQ-80 developers give approximately the same fog so that there is little to choose betw^een these developers. It has been shown that if there is a tendency for aerial fog by virtue of exposure of the film to the air as a result of frequent examination of the film during development, a pyro developer or one containing pyro is to be preferred on account of the anti-aerial fogging action of the oxidation products of development.
1 Mees, C. E. K., The Color Sensitivity of Photographic Materials, "J." Frank. Inst., May 1926, p. 525.
2 Jones, L. A. and Sandvik, Otto. Spectral Distribution of Sensitivity of Photographic Materials, "J." O. S. A., If, April 1926, p. 401.
3 Jones, L. A. Incandescent Tungsten Lamp Installation for Illuminating Color Motion Picture Studio, 'Trans." S. M. P. E., No. 22, 1925, p. 25.
^Benford, Frank, The High Intensity Arc, 'Trans." S. M. P. E. No. 24, 1925, p. 71.
sLuckiesh, M., The Physical Basis of Color-Technology, ''J. "Frank. Inst., July 1917, p. 85.
6 Gage, H. P., Colored Glasses for Stage Illumination, 'Trans." S. M. P. E., No. 18, 1924, p. 37.
7 Dundon, M. L. and Crabtree, J. I., The Effect of Desensitizers m Development,'Trans." S. M. P. E. No. 26, p. 111. ^ ^
8 Crabtree, J. L, The Development of Motion Picture Film by the Reel and Tank Systems, "Trans." S. M. P. E., No. 16. p. 163.
9 Dundon. M. L. and Crabtree, J. I., The Fogging Properties of Developers, "Brit. J. Phot.," 7i, 719, 1924