196 



PHO TO-MICROGRAPHY. 



\CH. VIII. 



should be used. The focusing screen as thus prepared with a clear 

 center, serves both for the general focusing and the finest focusing, and 

 avoids the danger of using a double screen. That is, the fewer the 

 processes the less the liability to error. 



Fig. 151. Perie,raphic Objective of about go millimeters equivalent focus for 

 making photo-micrographs at a magnification of 2 to 15 diameters. It was found 

 to give the best results when used right end to as in ordinary photography. [From 

 the Gundlach Optical Co. ) 



Fig. 152. Zeiss' Anas- 

 tigmat Objective of about 

 85 millimeters equivalent 

 focus for photo-micro- 

 graphs at a magnification 

 of 2 to is diameters. Ex- 

 cellent results were ob- 

 tained ivith this, and the 

 other short focused anas- 

 tigmats. On the zvhole 

 the results ivere more sat- 

 isfactory when the lens 

 was used right end to as 

 in ordinary photography. 

 [From the Bausch and 

 Lomb Optical Co.) 



§ 337. Development of the Negative. — After the exposure, comes 

 the development ; this in photo-micrography requires more judgment 



