196 



PHO TO-MICROGRAPH Y. 



[CH. VII 7 



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. Perigraphic 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 

 Me Gundlach Optical Co. ) 



Fig. 152. Zeiss' Anas- 

 dig-mat Objective of about 

 S5 millimeters equivalent 

 focus for photo-micro- 

 graphs at a magnification 

 0/2 to 15 diameters. Ex- 

 cellent results were ob- 

 tained with this, and the 

 other short focused anas- 

 tigmals. On the whole 

 the results were 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 



