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HANDBOOK OF PHOTOGRAPHY 



The apertures suitable for photography with photoflash lamps when the shutter is 

 opened during the flash is given in Table XX. If synchronized flashes are used, the 

 next larger aperture (next smaller /-number) should be used. 



Table XX. — Exposure for Color Photography with Photoflash Lamps 

 (Weston Rating — 4 to 8) 



* See note 3. 



Table XX gives the suggested exposures for still color photography with photoflash lamps with 

 various reflectors and for various distances between the subject and the lamp. 



1. Film Speed. — Table XX is based on the use of film having a tungsten speed rating of Weston 

 4 to 8, such as Dufaycolor or Kodachrome. For other film speed, 



multiply /-number by 2.5 for Weston speeds between 0.6 and 



" 1.6 ' " 1.5 " 



1 " 4 



" 0.6 " 10 



0.4 " " " " 24 



1.2 

 3 



2. Lamps. — It is assumed that only one lamp is used. If n lamps are used in the same distance 

 from the subject, multiply the apertures given by -y/n- For example, if four No. 10 lamps without 

 reflectors are used 8 ft. from the subject, the required aperture will be//4 X -v^ = //8. 



3. Reflectors. — When reflectors are used, e.xposure depends to a large extent on the angle over which 

 the light is distributed. Consequently, the values given should be regarded merely as suggestive for 

 average conditions. • 



Tables for Black-and-white Motion-picture Photography. — Fundamentally the same 

 laws of exposure apply to motion-picture as to still photography with the exception 

 that a sufficient number of pictures must be taken per second to reduce flicker to a 

 minimum and give a sense of motion when the individual frames are projected. In 

 practice, this means that about 16 to 24 frames per second must be made, so that it is 

 manifestly impossible to give an exposure time longer than from Ke to J^4 sec, and 

 usually in practice the actual exposure is more likely to be between 3-^0 and J^o at 16 

 frames per sec. Since the shutter speed is, furthermore, fixed or adjustable in wide 

 steps, it is necessary to make changes in the exposure by means of varying the aperture. 



Table XXI gives basic exposure for motion-picture photography in black and white 

 with daylight illumination. 



