February, '12] O'KAXE: INSECT PHOTOGRAPHY 55 



slides. On the platform rests an ordinary, compound microscope 

 which happened in this case to be ancient and discarded. The 

 photographic lens is carried at the lower end of the tube of the micro- 

 scope. This tube was sawed off at the upper end so that the limits 

 of its bore would not interfere with the diverging light rays coming from 

 the lens. Connection is made between the microscope and the 

 camera proper by means of a black cloth tube. The object to be 

 photographed is placed on the stage of the microscope. The advan- 

 tages of this arrangement are as follows : The mechanical and revolv- 

 ing stage with which the microscope is fitted permits of moving 

 the object delicately and smoothly into the center of the field of 

 vision. The focusing is done by moving the lens tube up and down 

 with the ordinary focusing screw, thus avoiding disarranging or jarring 

 the object. The bellows are previously extended to whatever point 

 is desired in order to obtain the magnification wished for, the stand 

 itself having been marked at the various points at which the plate- 

 holder should rest to give certain magnifications. This method of 

 getting the object into the field and into focus has been found rapid 

 and satisfactory. 



The third camera is a regulation 5x7 field outfit. 



Lenses. With the large camera first described a set of Zeiss Protar 

 lenses are used. There are three compound lenses, the focal depths 

 of which are 13 3-4, 11 3-16 and 8 3-4 inches respectively. Any of 

 these may be used singly, or any two may be used in combination. In 

 the latter case the resulting lenses have much shorter focal depth. 

 Tlje single lenses are used for copying and moderate enlarging. The 

 combination lenses are adapted to field work, where the object is com- 

 paratively remote from the lens. Nine times out of ten in photo- 

 graphing an insect or its work at same size or at enlargements of two 

 or three diameters we use the 11 3-16 inch lens, and if one has a sepa- 

 rate field camera fitted with its own lens, this size alone will serve all 

 ordinary needs. 



With the second camera we use a Bausch and Lomb Micro-Tessar, 

 size 48 mm. , made especially for this kind of work. The principal 

 desideratum is a lens so constructed that it ^\i\\ have as much focal 

 depth as possible; that is, one that wtII bring out sharply the nearest 

 and the farthest parts of an object, even at considerable magnification, 

 as for example the antennae and the feet of a beetle. The ordinary 

 lens will not do this: the regular objective of a microscope least of all. 

 Furthermore, for successful work of this nature the lens must contain 

 within its mounting a diaphragm, by means of which, after focusing, 

 the aperture may be reduced and details brought out that would 

 otherwise be lost. 



