622 HANDBOOK OF PHOTOGRAPHY 



The following is the usual procedure : An incandescent light source over which can 

 he placed in succession the three standard color-separation filters should be arranged 

 conveniently in the darkroom. Five pieces of the negative material to be tested 

 should be exposed, each for the same length of time, in contact with the photometric 

 wedge with the red filter in front of the light source. A similar number of exposures 

 are to be made with the green and with the blue filter, allowing, of course, for the 

 proper filter factor. When all the exposures are complete, each group can be put away 

 temporarily in a lightproof box w^hile preparing for development. Of course, the 

 negatives of each group must be properly identified with respect to the other groups. 



The rate of development is materially affected, not only by the composition and 

 temperature of the developer, but also by the agitation during development. Further- 

 more, a moderate amount of agitation is necessary in order to prevent irregularities 

 and streaks around areas of heavy exposure. The most satisfactory method is to use 



Fig. 9. — Densitometer for measuring the transmission density of films or the reflection 



density of prints. 



a tank appreciably larger than for ordinary black-and-white negatives. With 5- by 

 7-in. negatives, for instance, the 1-gal. hard rubber tank with the regular No. 4 East- 

 man developing hangers is very convenient. Use it for onlj^ six negatives at a time 

 with the standard pyro ABC developer made up as recommended, i.e., 9 oz. each of 

 A, B, and C and water to make up 1 gal. at a temperature of 68°F. The six negatives, 

 which are first loaded in the hangers, are immersed all together in the developer, pulled 

 out of the developer, reimmersed all together twice, and then pushed all together 

 toward one end of the tank. Then one by one the negatives are slid toward the 

 opposite end of the tank and so on back and forth until the time of development is up. 

 During these back and forth movements, the negatives should always be maintained, 

 fully immersed in the developer. At the completion of development the negatives 

 are lifted out all together, given a brief rinse, and then immersed in the fixing bath. 

 For carrying out the development test with the negatives exposed behind the 

 photometric wedge described, the following is a convenient procedure: The developer 

 is carefully compotmded and its temperature adjusted to 68°F. Three tanks con- 



