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HANDBOOK OF PHOTOGRAPHY 



Exposure Devices. Exposure Calculators. — Exposure calculators in the form of 

 .sliding scales or disks which may be rotated with respect to other marked scales, 

 usually cover a wide range of light conditions, film speeds, aperture, shutter speeds, 

 and sometimes give additional factors affecting exposure such as filter factors. 



Table XXII. — Basic Exposure for Black-and-white Motion-picture 



Photography, Photoflood Illumination 



(Weston Ratings— 10 to 20) 



Table XXII gives the suggested exposure for black-and-white naotion-pieture photography using 

 photoflood illumination. It is based on the following conditions: 



1. Film Speed. — Calculated for films having a tungsten speed rating of Weston 10 to 20. For 

 converting to other film speeds, 



multiply aperture by 0.25 for Weston speeds between 0.0 and 1.2 

 " 0.4 

 " 0.6 

 " 1 

 " 1.5 

 "2.5 

 '■ 4.0 



2. Lamps. — Number of lamps as indicated. It is assumed that polished-metal reflectors are used. 



3. Subject Matter. — It is assumed that subjects of average brightness are being photographed. 

 If light subjects are photographed, the exposure may be reduced somewhat, whereas if dark subjects 

 are being photographed, the exposures should be increased. 



4. Shutter Speed. — As indicated. For standard speed of 16 to 24 frames per second. 



