W. SI. GRAHAM — THE PHOTOGRAPHY OF DIPTERA. 



157 



a backgrouud and to i-euder tlie outlines of the insect distinct. If the hght 

 reflected by it be too strong the surface markings of the insect are rendered 

 indistinct. The lighting from behind must therefore be completely subordinated 

 to that from the front, supplied by the window and by the two mirrors. The 

 object of the square mirror on the base-board is to Kght the head of the insect 

 which, as already emphasised, should always be arranged upon the easel head 

 downwards. The object of the side mirror is to hght the side of the insect 

 which would otherwise be in shadow. 



Fig. 2. — Arrangement of mirrors and reflector for illumiuating the object 

 to be photographed. 



The more oblique the lighting the greater relief of the picture, but care is 

 necessary to avoid reflections from shiny surfaces, especially in black insects. 

 For the production of a successful negative the lighting must be so arranged that 

 the outlines are sharp, and that as much relief is obtained as is possible Avichout 

 causing any reflections. If the lighting is correct the picture on the ground- 

 glass wiU have these three qualities. If the details of the picture on the ground- 

 glass be indistinct the lighting is wrong and requires alteration. 



Magnification. 



The insect is now ready to be photographed, and the amount of the magnifica- 

 tion desired should be decided. This will depend upon the size of the picture, 

 which will again be conditioned by the size of the plate employed. I have found 

 quarter-plate a suitable size. 



The amount of the magnification being decided upon, it only is necessary to 

 place the front and back of the camera in correct relative positions. To do this 

 it must be remembered that the distance from the lens to the insect must bear a 



