1 32 PHOTOMICROGRAPHY 



To Take the Photograph. Place the object in such a 

 position that it is illuminated to the best advantage, 

 and adjust the lamps, reflectors or condensers until the 

 required amount of shadow is obtained. Refer to the table 

 of enlargements for the camera extension and distance 

 between object and lens to give the desired magnification, 

 adjust the camera accordingly. Roughly focus, and move 

 the object until its image falls within the limits of the 

 plate, as indicated by the lines drawn on the ground glass, 

 altering the magnification if necessary. Colour screens 

 are sometimes of advantage ; when used they are placed 

 between the object and lens or behind the lens. The 

 principles governing their use are discussed in Chapter IX. 

 Carefully focus the image on the ground glass, and close 

 the iris diaphragm until the necessary depth of focus is 

 obtained ; a lens should be at hand forexamining the image 

 on the ground glass. The dark slide, with plate in position, 

 is then placed in the camera/assurance made that the lens 

 is capped or covered, and the slide drawn, every care 

 being taken to prevent any disturbance of the camera. 

 Exposure is then made by means of the shutter, or by 

 moving the cap, or in its place a piece of card held in 

 front of the lens. The slide is then replaced, and the plate 

 taken to the dark room and developed before the appara- 

 tus is disturbed. Time is frequently saved thereby, as any 

 errors in exposure, focus, etc., can be detected during 

 development, or on examination of the plate after fixation, 

 and a second exposure made if necessary. When certainty 

 has been obtained by experience time is saved, however, 

 by making all the exposures necessary one after another, 

 and developing the plates all together in a tank, or two 

 or three at a time in dishes. 



The question of exposure is discussed in Chapter X, 

 but the exposures given in the descriptions of the 

 illustrations will serve as a rough guide to the times 

 necessary. 



