82 



HANDBOOK OF PHOTOGRAPHY 



More elaborate finders are arranged to indicate to the photographer when his 

 camera is properly focused as well as to show him the field of view that is being covered. 



Light scaHered 

 in all olireclions 



Real image 

 /A--' o n ground 

 " glass 



- Camera 



I I Oblique 

 ' ' ligh-tra^jS 

 beni and 

 confined fo 

 a narrow 

 cone 



Real image 

 in Ihis lens 



MirrorU- Camera 



Ground Glcjtss Finder Brillian+ Finder 



Fig. 10." — Common types of finders. 



Objeci 



Image Image j 



Ay Ay 1-2^ 



L8cU Li 



The field seen through the finder is often smaller than that actually covered by the 

 lens, so that the user is certain of getting into his picture all that he sees in the finder. 

 The fact that the lens of the camera and the lens of the finder do not view the subject 

 from the same point is not a serious matter unless close-ups are made. Errors due to 



separation of the two lenses are minimized 

 by placing the finder as close as possible to 

 the camera lens and by making the finder 

 axis and the camera axis intersect at about 

 15 ft; in front of the camera. 



Parallax. — Certain view finders auto- 

 matically compensate the error arising from 

 parallax which causes the picture as actually 

 registered on the sensitive material to be 

 different from that seen in the view finder. 

 As the camera is brought close to the object, 

 the view is restricted by a mask which is 

 mechanically connected with the coupled 

 range-finder mechanism. In general, however, the photographer must be careful 

 to include the desired object in the center of his composition when working 

 up close to the object and when relying upon the view finder to determine what is 

 actually being photographed. If the camera is equipped with a ground glass, it will 

 be much safer to make the actual composition by this means than to rely upon the 

 view finder. 



Focusing Scale. — Cameras of the focusing type must use a focusing scale unless 

 the operator is to focus his scene on a ground-glass screen each time he makes an 

 exposure or unless he has an "automatic focus" type of coupled range finder. All but 

 reflex, view, and studio cameras employ a focusing scale which may be used or not as 

 the owner of the camera desires. With lenses of long focal length it is more important 

 to estimate distance accurately than with short-focal-length lenses because of the 

 shallower depth of field of the former. If the negatives made by the short-focal-length 

 lens are to be enlarged to the same size as those produced by the longer lens, the 

 accuracy of focusing must be the same. 



Fig. 11. — Use of negative lens to form 

 virtual image in front of lens L\ which is 

 then projected to a comfortable position 

 with respect to the eyes. 



