672 



HANDBOOK OF PHOTOGRAPHY 



standard negative, a higher gamma results, and the background print, when developed 

 to the regular positive gamma, provides the higher contrast desired. 



Duplicate negatives are made for protection against loss of the original negative or 

 excessive wear on it, for release printing in foreign countries, for optical printer treat- 



0.6 L2 1.8 Z4 3.0 56 

 Log Exposure (reiativej 



Fig. 12, a. — D-logio ^ curves of DuPont 

 Superior panchromatic negative No. 100. 



2 4 6 8 10 12 14 

 Minu+es- 



FiG. \ZB. — Time-gamma curve of DuPont 

 Superior panchromatic negative No. 100. 



Fig. 13C — Spectrogram of DuPont Superior panchromatic negative No. 100 (daylight). 



3.6 



Fig. 



0.6 1.2 1.8 24 3.0 

 Log Exposure (relative^ 



14A. — D-logio.B curves of DuPont 

 duplicating negative, type 107. 



2 4 6 8 10 12 14 

 Minu+es 

 Fig. 14B. — Time-gamma curve of DuPont 

 dupHcating negative, type 107. 



ment, etc. The procedure involves printing a master positive on special stock, from 

 which the new negative, likewise on special stock, is made. The approved duplicating 

 technique involves operating at a relatively low negative gamma (0.5 to 0.6) and a high 

 positive gamma (1.8 to 2.0) to avoid excessive negative grain. (The negative mate- 

 rial is susceptible to grain with higher gammas, while the positive grain remains rela- 



