Photomicrography 



53 



Figs. 64, 65, and 66. Three cameras corresponding to the diagrams in Figs. 61, 62, 



and 63. Fig. 64 is a Bausch and Lomb model H camera corresponding to the diagram 

 in Fig. 61. Fig. 65 is a Leica "Ibso," corresponding to the diagram in Fig. 62, mounted 

 on a Bausch and Lomb model DDE microscope. Fig. 66 shows an American Optical 

 Company trinocular "Microstar" microscope and camera corresponding to the dia- 

 gram in Fig. 63. 



size the latter may be. The area to be photographed is therefore en- 

 tirely dependent on the objective selected and, usually, only the central 

 portion of this area is in critical focus. It is also, compared to the next 

 method, inconvenient to have to swing the mirror out of place before 

 making the exposure. 



Split-beam-image Projection (Figs. 63 and 66). A regular, inclined 

 binocular microscope has a beam-splitting prism built in over the objec- 

 tive. The rays that will form the image are thus split into two components. 

 One portion passes directly upward toward the film, being interrupted 

 only by a shutter to control the exposure. The other component is diverted 

 toward the regular observational oculars. 



The advantages of this system are enormous. To take a photograph, 



