MOTION-PICTURE PHOTOGRAPHY 



671 



SO 



2.0 



?^ 



The data for the above films are in general self-explanatory in the light of wliat has 

 been said previously about ordinary, orthochromatic, and panchromatic emulsions. 

 The special-purpose emulsions, however, 

 require additional comment. These com- 

 prise the duplicating negatives (Eastman 

 1503 and 1505; DuPont 107) and the back- 

 ground negative (Eastman 1230). 



The latter is used in making "keys" or 

 "plates "for process photography (see Process 

 Photography) . Usually these represent out- 

 door scenes, such as streets with traffic or 

 bodies of water, which are rear-projected on 

 a translucent screen and rephotographed in 

 combination with foreground action. For 

 such a purpose it is desirable to utilize a 

 negative having about the same color 

 characteristics and latitude as standard 

 negative, but of extremely fine grain, since 

 graininess is one of the principal obstacles to effective use of process backgrounds. 

 The fineness of grain is secured at some sacrifice of speed. The contrast of back- 



1.0 



3.0 3.6 



Fig, 



06 (.2 1.8 2.4 



Log Exposure (relative) 



12^. — Z)-logio E curves of DuPont 

 panchromatic negative No. 116. 







1 



10 12 



4 6 8 



Minufes 



Fig. 125. — Time-gamma curve of DuPont panchromatic negative No. 116. 



Fig. 126'. — Spectrogram of DuPont panchromatic negative No. 116 (daylight). 



Fig. 12D. — Spectrogram of DuPont panchromatic negative No. 116 (tungsten). 



ground negative is high enough to compensate for losses and stray-light interference 

 in projection. The background negative being developed for the same time as 



