PHOTOGRAPHIC EQUIPMENT 41 



and field work in general is a 7i/2-inch Protar F. 7. con- 

 vertible anastigmat with a 11%-inch back and a 13%-inch 

 front element focus, this fitted to a volule shutter work- 

 ing from time to 1/150 second, with thumb, bulb and pull 

 release. 



I use the telephoto lens on this camera. This lens is 

 an Adon, working at F. 15 with a bellows extension of 

 5 inches and giving a magnification of three times at this 

 extension as compared to a lens of 5-inch focus, or the 

 equivalent focus of a lens of 13-inch focus. When at 

 22-inch focus, it gives an F. value of 55, an equivalent 

 focus of F. 45 and a magnification of 9 diameter. 



The Adon telephoto lens is composed of a front 

 cemented doublet of 4i/2-inch positive focal length, and a 

 back negative cemented doublet of 2-inch focal length. 

 The separation of the elements is governed by a rack and 

 pinion movement. This lens is complete within itself; 

 hence it requires no other lens and thus gives better illu- 

 mination and more speed than if used as an attachment 

 to another lens. 



The entire Adon weighs only five ounces. In brief, 

 this lens gives a picture three times the size of any other 

 lens at an equal bellows extension. For the benefit of 

 anyone who may wish to purchase an Adon the following 

 table is inserted : 



Lin. mag. As eomp. 

 as comp. with Time Reg. Adon 

 with 8-rii. Lens Camera Stop 4 

 5-in. Lens 

 Diameter Diameter Sec. Sec. 



31/2 3 1/11 1/3 



5 31/2 i/s 4/5 



6 4 1/4 1 



7 1/2 2 



8 5 



9 % 3 

 10 

 11 8 1 4 



All shutters used with any lens should be as free 

 from noise as possible. 



In using the Adon with this long bellows extension 

 there must be no vibration of the camera, either from a 

 shaking tripod or jarring shutter blades, as the exposures 

 are from two to eight seconds long. This lens can be 



