ADAPTING A SHORT-BELLOWS, ROLL-FILM KODAK 

 FOR DETAIL WORK IN THE FIELD 



CHESTER K. WENTWORTH 



University of Iowa 



Most geologists, when in the field, have occasionally felt the 

 need of a portable camera with which they might take large-size 

 detail photographs. The ordinary equipment for such work, the 

 long-draw, box camera, is far too heavy and bulky to be carried by 

 the geologist as a part of his daily accoutrement. The roll-film 

 kodak with the customary short bellows which is most convenient 

 for his usual needs, fails when he wishes a picture larger than about 

 one-tenth natural size, and the auxiliary portrait lens does not 

 greatly increase the scope of his outfit. If he wishes a detail picture 

 of a fossil in place, a curious marking or texture of a rock which 

 cannot be conveniently sent to his headquarters, he must note the 

 place and come again later with the more bulky equipment. He 

 almost never does. 



The device described below has been found by the writer to be a 

 simple and convenient solution of the problem. An auxiliary por- 

 trait lens was first secured to fit the kodak he wished to use. This 

 attachment consists of a simple plano-convex lens of about 52-inch 

 focus. When placed close in front of the kodak lens this causes 

 parallel beams of light to become slightly convergent when they 

 strike the main lens system and thus shortens the focus of the com- 

 bination (See Fig. i. Scale II). With the principal focus now some- 

 what nearer the ground glass, the slight additional excess of bellows- 

 length permits focusing on closer objects and hence larger pictures 

 than with the kodak lens only. 



Next, there were procured from an optician two more lenses of 

 foci approximately 16 inches and 8 inches respectively. These 

 were ground to the proper diameter to fit the cell belonging to the 

 original auxiliary. The three lenses are readily interchangeable by 

 unscrewing the ring which holds in place the lens used. By using 



