76 HANDBOOK OF PHOTOGRAPHY 



accordingly. The camera may make a single exposure, or it may carry enough film 

 to make 36 exposures. The lenses are fairly well corrected. Some are equipped with 

 masking devices so that, on a given film, two sizes of pictures may be made. Cameras 

 of this type, equipped with large-aperture lenses, produce good results in the hands 

 of those who can estimate or measure distance accurately. In general, however, 

 the user cannot expect to enlarge his negatives as much as negatives made with 

 cameras having coupled range finders and lenses with greater correction. These 

 small guess-the-distance cameras are not comparable with the second group for the 

 serious photographer. 



In the second group are those cameras which represent the acme of manufacturing 

 precision. In size of picture made, they range from the 24- by 36-mm. negative made 

 on 35-mm. standa d motion-picture film to 2}^ by 3J^ in. They utilize coupled range 

 finders. They are fitted with lenses with very high correction, often arranged to be 

 interchangeable with other lenses of shorter or longer focal length. In the Leica, 

 Contax, Exakta, and similar types of cameras a focal-plane shutter operating at 

 speeds up to H250 sec. is supplied. The accuracy of adjustment and the correction 

 of the lenses is so great in these cameras that enlargements of 10 to 30 times are not 

 out of the ordinary at all. In a few cameras, roll film, cut film, or plates may be used. 

 Many accessories are available for cameras of this general class, which extends the 

 possibilities of the camera. The user need not purchase anything but the camera and 

 lens, however, to have a complete outfit. The additional lenses, and other accessories, 

 will cost a great deal more than the camera itself and form desirable equipment which 

 can be accumulated over a period of time — or never purchased at all. An important 

 feature is the mechanical coupling between the shutter-cocking mechanism and the 

 film-advance mechanism, making it impossible to make double exposures. 



In the third group are the reflecting cameras. Some of them have a single lens; 

 others have two lenses, one for focusing and one for making the exposure. In general 

 these cameras do not have interchangeable lenses, although front lenses may be used 

 to reduce or increase the focal length of the taking lens. Certain models, however, are 

 equipped so that the lenses may be changed for others of longer or shorter focal length. 



In the Contaflex of Zeiss Ikon the focusing lens brings the image, not to a ground- 

 glass screen, but to a plano-convex lens of rectangular shape, the underside of which 

 is matted. The image is "brilliant" to the corners. For critical focusing a magnify- 

 ing lens can be swung into position over the image. This latter feature is character- 

 istic of several of the miniature reflex cameras. In addition, the Contaflex has a 

 built-in photoelectric exposure meter. 



Certain two-lens cameras are not reflex types. The second lens is merely a view- 

 finder lens and is not connected mechanically with the taking lens. The second lens 

 makes it possible for the user to see an image of his scene full size and right-side up by 

 means of a reflecting mirror. The finder lens is of fixed focus and is not connected 

 with, or related to, the taking lens. The latter must be set to the correct focusing 

 position after the user has estimated or measured the distance of the subject from the 

 lens. 



Optical and Mechanical Requirements for Miniature Cameras. — Speaking before the 

 Photographic Society of America, Rochester, 1938, H. W. Zieler discussed the maxi- 

 mum inaccuracies that may exist in manufacture and alignment maintenance in a 

 high-grade camera making a negative 1 by 1 J^ in. in size. He stated that a 2-in. lens 

 at 33^ ft. at an aperture of //1. 5 must be focused with a maximum tolerance of 

 0.001 in. The focal length of the lens must be matched to the focusing mechanism 

 to within 0.001 in. The total variation from all causes in the mechanical dimensions 

 of the coupled range finder must not be over 0.001 in. 



