EXPOSURE AND EXPOSURE DEVICBS 



239 



/o. The exposure for any film having a Weston speed of 24 to 48 will be found in 

 Table XV for the aperture / at which the photograph is made. This table is suitable 

 for use with black-and-white or color photography so long as proper correction is made 

 for film speed and the light employed is suitable for color photograph}^ 



Table XV. — Use of Diaphragm Aperture in Determining EIxposure 

 (Weston Rating— 24 to 48) 



The tables are calculated for films having a speed of Weston 24 to 48. For films having other speeds 



Exposures for outdoor photography at night are given in Table XVI. The table 

 is based on a film having a speed of Weston 8 and applies for various types of sub- 

 jects. Values of exposure are given for apertures of from //2*to //32, but data for 

 other apertures may be determined by interpolation, or by means of Eq. (23). 



Table XVII gives the maximum exposures for moving objects which will "stop 

 motion " in the photograph when a lens of 5- or 2-in. focal length is used. Corrections 

 for other focal lengths may be made in the manner indicated at the bottom of the table. 

 The shutter speeds given are based on the relative apparent speed of the object across 

 the camera field and do not bear any relation to the shutter speed which may be 

 required for proper exposure. The shutter speed required for exposure may be deter- 

 mined from other tables or by exposure meters, but Table XVII gives the limiting 

 shutter speeds if sharp outlines are desired for moving objects. 



This table should be used in conjunction with exposure tables when photographing 

 moving objects. It is, perhaps, best to determine the shutter speed from Table XVII 

 for the type of moving subject being photographed, after which the aperture and film 

 speed for this shutter speed may be determined. For example, if we are photograph- 

 ing a small boat moving 10 m.p.h. (approximately 9 knots) obliquely across the field 

 when it is 25 ft. from the camera, the shutter speed required for a 5-in. lens will be 

 J-2 sec. By reference to Table VIII, we find that the subject matter falls into 



