232 



HANDBOOK OF PHOTOGRAPHY 



factor 3/1.5 = 2, so that for taking a picture in New York at 5 p.m. in June, the correct 

 exposure time would be 3^ sec. if Ho sec. were correct for the exposure at 10 a.m. 

 Table X gives basic exposure data for indoor photography using daylight only. 

 Like Table VIII it has been reduced to the simplest possible form, and consequently 

 should be regarded as being suggestive rather than providing exact data. It may be 

 used for films having speeds of Weston 10 to 20 without correction. The tables are 

 calculated for that part of the day in which the intensities of daylight are greatest. If 

 desired. Table X may be corrected with the data provided by Table IX. 



Table VIII. —Exposures for Black-and-white Still Photography in Daylight 



(Weston Rating— 24 to 48) 



This table shows recommended exposures for four different types of subjects and five different sky 

 conditions which are typical of conditions likely to be encountered. 



1. Light Values. — The light values are calculated for those conditions for which the light value in 

 Table IX is unity (1). For other light values, multiply the shutter speed by the factor given in Table 

 IX. The corrections for sky conditions are in addition to those given in Table IX for various latitudes 

 and times of day. 



2. Film Speed. — Tables are based on daylight film-speed rating of Weston 24 to 48. For other 

 Weston film ratings, the shutter speed is inversely proportional to the Weston speed. 



3. Time of Day. — Table applies to within 1 hr. of sunrise and sunset for panchromatic materials or 

 within 23-2 hr. of sunrise and sunset for orthochromatic materials for all latitudes up to about 55". 

 For greater latitudes the tables cannot be used so close to sunrise or sunset without additional exposure. 



4. Aperture. — Recommended exposures for five standard apertures are given. For converting to 

 other apertures, see Eq. 23. 



