EXPOSURE AND EXPOSURE DEVICES 



Table XVII. — Exposure for Moving Objects 



241 



Speed, 

 m.p.h. 



0-1 



2 

 3 



4 



10 

 15 

 20 

 30 

 40 

 60 

 80 

 100 



Typical subjects 



Landscapes, sea scapes, street 



groups 



Slow-walking pedestrians 



Walking pedestrians 



Fast-walking pedestrians 



Slow cyclists 



Slow vehicles in heavy traffic 



Cyclists, trotting horses 



Slow street traffic 



Automobiles (city traffic) 



Automobiles 



Automobiles 



Trains, automobiles 



Fast trains 



Airplanes 



2-in.-focal-length lens 



Objects 

 moving 

 directly 

 toward 

 camera 



Objects 

 moving 

 obliquely 

 across 

 field of 

 view 



Objects 

 moving 

 across 

 field of 



5-in.-focal-length lens 



Objects 

 moving 

 directly 

 toward 

 camera 



Objects 

 moving 

 obliquely 

 across 

 field of 



Objects 

 moving 

 across 

 field of 

 view 



Exposure time, sec. 



K2 



Ks 



Ms 



Mo 



Ho 



Veo 



Mo 



M25 



Hso 



M50 



Moo 



Moo 



Mo 



Mo 



Moo 



M25 



3-^00 



Mso 



Moo 



Moo 



Moo 



Mooo 



M^oo 



Mooo 



3-^4 00 



Mooo 



Table XVII gives the maximum exposures which may be given, if sharp images are desired, for two 

 lenses of different focal length, and for various speeds of moving objects. The table is based on an 

 assumed distance of 25 ft. between the camera and the moving object, but conversions may be made for 

 other conditions. For example, let So be the shutter speed given for the 5-in. lens. Then the shutter 

 speed S for other distances between camera and subject d and for lenses of focal length I ia 



S = -So 



(0(1) 



The distance d is in feet, whereas I is in inches 

 longest permissible exposure is 



2400 



Thus, for fast trains at 100 ft. with a 2-in. lens, the 



- (I) X (f ) = 



10 

 2400 



1 



240^ 



if the train is traveling across the field of view. 



Table XVII bears no connection to the shutter speeds required by light conditions to give the 

 necessary exposure to the film; it simply gives the longest exposure permissible which may be expected 

 to "stop motion." Table XVII should then be used with other tables to determine the aperture and 

 shutter speeds required to give the proper exposure to the film for existing light conditions. 



Tables for Still Color Photography. — So long as the reduced speed and additional 

 color sensitivity of color films are properly taken into account, the tables for black-and- 

 white still photography could be used for still color photography. However, it is 

 convenient to have tables which automatically take these factors into account. 



Table XVIII gives basic exposure data for still color photography in somewhat 

 the same way that Table VIII gives similar data for black-and-white photography. 

 For shutter speeds or apertures which are not given, extensions to the table may be 

 made in the manner already described. The table is based on film speed of Weston 

 4 to 8 which applies to the present Kodachrome and Dufaycolor film in daylight. 



