230 HANDBOOK OF PHOTOGRAPHY 



For convenience in use, the tables are divided into the following sections: 



1. Black-and-white still photography. This section includes much basic data 

 which is also applicable to other types of photography. 



2. Color still photography. 



3. Black-and-white motion-picture photography. 



4. Color motion-picture photography. 



Within each group will be found representative, or basic, exposure data which may 

 be used as a guide for various lighting conditions including lighting by photoflood, 

 Mazda, and photoflash lamps, as well as by daylight. 



Conditions for Which Tables Are Determined. — -The basic exposures given in the 

 following tables are recommended as being approximately correct for the conditions 

 stipulated in the title; additional conditions for which the tables apply will be found 

 in the notes at the bottom of each table. In general, the tables are determined for 

 those film speeds, apertures, shutter speeds, and lighting conditions which are believed 

 to be most typical and consequently most frequently used. However, the exposure 

 tables may be extended to apply to other conditions not listed but which the photog- 

 rapher may elect to use for some particular reason or another. The tables of basic 

 exposure may be extended to apply to conditions other than the typical conditions by 

 making the necessary alterations for various film-speed ratings, apertures, shutter 

 speeds, and filters derived from Eq. (18). 



In establishing the data for these exposure tables, it was desirable that some 

 method be adopted to express the speed or sensitivity of the various types of emulsions 

 which might be used in practice. Because of the soundness upon which the method is 

 based, the excellent results which practical photographers have achieved using it, its 

 rather extensive adoption in the photographic field, and the comparative ease with 

 which the photographer can obtain speed ratings of a wide range of emulsions, the 

 Weston film-speed rating has been chosen as the standard in the determination of the 

 exposure tables.^ The table of film-speed ratings given in Appendix B will assist 

 the photographer in determining the speed of the film used. 



Tables for Black-and-white Still Photography. — Listed among the tables giving 

 basic exposure data for monochrome still photography are a number of tables which 

 apply equally well to color or to motion-picture photography. They are included here 

 since it is intended that this section give as much fundamental data on exposure as 

 possible. The tables in other following sections of this chapter apply to those special- 

 ized cases where the specific type of photography demands a somewhat different treat- 

 ment of exposure than can be given here. 



Table VII gives the relation between the aperture (in both the / and the uniform 

 systems — U. S.) and the relative exposure. The table may be used to convert an 

 exposure with any given aperture to the exposure time required for an entirely differ- 

 ent aperture, by forming a simple ratio. For example, suppose the tables of exposure 

 indicate that the proper basic exposure is to = J^o sec. at an aperture /o = 8, but that 

 we desire to find the exposure for an aperture / = 5.6. The relative exposure for 

 / = 8 is 64, whereas for / = 5.6 it is 32. Since the aperture is increased in size, a 

 smaller exposure time will be required and will in fact be ^%4, times Ko or /4o sec. 



The absolute values of numbers in the third column have no significance, and were 

 chosen so that all figures would be greater than unity. The numbers have significance 



1 The photographer may make conversions to other methods of film speed, if he chooses, by means 

 of the table of relative speed values given in Appendix B. However, it is recommended that the factors 

 enumerated in Speed or Sensitivity, p. 190, be given careful and thoughtful consideration before the 

 tables are converted to other film-speed ratings, as the systems by which film speed is determined vary 

 widely. In any case the use of the Weston speed ratings is to be preferred to other speed ratings when 

 using the exposure tables in this chapter. 



