72 



HANDBOOK OF PHOTOGRAPHY 



and the ability to keep the subject from approaching too close to the lens. The 

 negatives will stand some enlargement, but not a great deal, naturally. 



Folding Cameras. — Next above the box camera in complexity is the folding 

 camera for roll film. This group comprises cameras from the very cheapest to the 

 most expensive. The simplest camera of this type has a lens which snaps forward into 

 fixed position when the front of the camera is opened. It is used, therefore, exactly 

 like a box camera with the advantage that it is more compact. Its lens operates at 

 about the same aperture as that in the box camera. 



With lenses of larger aperture and consequently of smaller depth of focus, some 

 means of focusing must be provided. The lens as a whole may be moved along a 

 track with a focusing scale in feet or meters placed alongside; or the lens may turn 



Fig. 4. — Single folding camera. 



m a threaded mount, or only the front element of a doublet may turn, with the distance 

 scale placed along a circular portion of the camera structure. 



Folding roll-film cameras are seldom equipped with lenses of greater aperture than 

 //6.3 or//4.5. One reason is the cost of such lenses, and another is the shallow depth 

 of field. When the camera at large apertures is focused upon a near object and 

 operated with the diaphragm wide open, the user must estimate the distance to the 

 subject with accuracy greater than that possessed by the average person. Since at 

 any aperture the required accuracy of adjustment of the lens-filni distance increases 

 as the lens-subject distance decreases, cameras of the type being described are seldom 

 equipped for working closer to a subject than 6 ft. If, however, a short-focal-length 

 lens is to be used, as in a miniature camera, the lens may have a larger aperture, and 

 focusing may be possible up to within 3 ft. of the subject. 



Thousands of miniature cameras with fairly large-aperture lenses but not equipped 

 with coupled range finders find their way to the secondhand market because the pur- 

 chaser cannot get sharp pictures — largely due to the lack of the necessary ability 

 to estimate distance. A purchaser of a miniature camera naturally expects enlarge- 



