172« 



Journal of Applied Microscopy 





LABORATORY PHOTOGRAPHY. 



Devoted to Methods and Apparatus for Converting an Object into an Illustration. 



PHOTOMICROGRAPHY. 



IV. Focusing the Instrument. 



With low powers and a good light, focusing by means of the image on the 

 ground glass is not difificult so long as the operator can reach the focusing screw. 



Fig. 1. 



Fig. 2. 



If the objective used is a o5 mm. or one of lower power and a camera extension 

 of four or five feet is to be used, for the purpose of getting depth of focus with 

 increased magnification, it becomes necessary to control the coarse adjustment 

 screw by some means. We used a rod on the camera table with pulley attach- 

 ment. This is of course detached when high powers are used. A lens is often 

 used to ascertain the focus on the ground glass ; it should for this purpose have 

 telescopic mounting or rest on legs so that it will be at right angles with the 

 image and at the same time remain firmly in focus ; but the more experience one 

 has the more I think he will rely on naked eye appearance. The beginner 

 should study the focus carefully with and without a ground glass in the path 

 of the rays, with and without a hand lens and with diaphragms of all sizes ; he 

 should compare the appearance on the ground glass with the appearance under 

 the microscope with correct illumination ; in no other way can he ever learn to 

 correctly illuminate and focus his object for photography. 



