CAMERAS 



79 



Focusing. — Usually focusing is accomplished by changing the lens-film distance 

 by moving the entire lens. The lens may sometimes be screwed into a threaded 

 mount instead of being moved by means of a bellows. In other cases only the front 

 section of the lens may be moved. As already indicated, certain simple cameras 

 have only two focusing positions of the lens, one for close-ups and one for distant 

 scenes. In either of these positions the lens acts as a fixed-focus lens. 



Rising Front. — The lens board may be raised above a median position so that less 

 of the foreground and more of the upper part of a picture may be included without 



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Fig. 7. — Typical adjustment of lens with respect to focal plane. 



tilting the camera, a method which produces bad perspective. Tall buildings may be 

 photographed in this manner, especially if the camera is equipped with a swing back. 



Falling Front. — The lens board may be lowered so that more of the foreground may 

 be included. 



Side Movement of Lens. — When the camera is placed so that the picture is to be 

 made the long way of the film, a rising and falling motion of the lens is made possible 

 by another adjustment. This sideways movement (when the camera is vertical) 

 can be employed to include more of the right or left of a picture without moving the 

 position of the film. 



Swing Back. — This adjustment permits the film to be tilted about a horizontal 

 pivot through the center (or some other line) of the film. By this means the top 



