580 HANDBOOK OF PHOTOGRAPHY 



camera is shifted the desired distance between views. This ehminates the necessity 

 for transposing the plates. 



As it is desirable that a stereograph be level, the more expensive cameras are fitted 

 with levels and the lenses are held in a sliding front which permits of a small vertical 

 displacement for centering objects slightl.v above or below the level of the lenses. 



A list of the chief types of camera on the market follows. The list is not complete 

 l)iit gives an idea of the field. 



Eho. An inexpensive box-type camera. 2}^- by S.^^-in. roll film, //ll lenses. 

 Fixed focus. Time and single-speed shutter. Direct-vision wire view finder. Sands, 

 Hunter & Co., London. (Price about $15 in England.) 



The Puck. Similar to the Eho. Central brilliant-type view finder. Messrs. 

 Thornton Pickard, London. 



Heidoscope. A high grade, precision camera. Plate changing box for twelve 

 plates. Two sizes: 



45 by 107 mm. Ziess Tessar lenses //4.5. Focal length, 5.5 cm. Ziess anastigmat 

 view-finder lens //3.2 centrallj^ located. Variable-speed shutter. Variable focus. 

 Lens caps. Spirit level. (Price about $270 in England.) 



60 by 130 mm. Ziess Tessar lenses //4. 5. Focal length, 7.5 cm. Ziess anastigmat 

 Adew-finder lenses //4.2. Other features the same as above. R. F. Hunter Ltd., 

 London. (Price about $290 in England.) 



RoUeidoscope. The 60 by 130 Heidoscope made for roll films. (Price about $260 

 in England.) 



Voigtlander. 45- by 107-mm. plate changing box for 12 plates. //4.5 lenses. 

 Focal length, 6 cm. Variable-speed, Compur sector shutters to >2 5o sec. Variable 

 focus. Lens caps. Spirit level. (Price about $270.) 



lea Plaskop. An inexpensive camera. 45 by 107 mm. six individual plateholders. 

 lea Novar anastigmat //6.8 lenses. 6-cm. focal length. Time- and single-speed 

 shutters. Direct-vision wire view finder. 



lea polyskop. 45 by 107 mm. Plate-changing box. Ziess Tessar lenses //4.5. 

 Compur sector shutters to Mso sec. Direct- vision view finder. Variable focus. 



lea Minimum Palmos. 60 by 130 mm. Folding-bellows type. Ziess Tessar 

 lenses //4. 5. Focal-plane shutter to Kooo sec. 



Verascope. Numerous types. 45 bj^ 107 mm. and 60 bj^ 130 mm. All have 

 plate-changing box. Standard, and roll-film adaptors, optional. Lenses //6.3 on 

 cheapest type; //4.5 on others. Central view-finder lens. Variable speed shutters. 

 Manufacturer — J. Richard, Paris. Agent — R. J. Fitzsimons, 75 Fifth Ave., N. Y. 



Other sizes and types of camera, many having been made to order, many of dis- 

 continued makes, can be obtained secondhand by watching photographic periodicals. 



Viewing Instruments. Viewing without Aid. — The viewing of stereographs with- 

 out the aid of some form of viewing instrument always causes eyestrain. With con- 

 siderable practice it can be done with a fair amount of ease but is certainly never to be 

 recommended as a common practice. The judgment of depth by this means is never 

 accurate. This was discussed on page 572. 



If it is desired to experiment with this form of viewing, a piece of cardboard or 

 other flat shield should be placed normal to the two views and between them to render 

 them mutually exclusive to the two eyes. Without this shield three views will be seen 

 of which the center one will be the stereoscopic image. 



In this form of viewing the two views will seem to draw together until they are 

 superimposed. It is helpful to fix on some prominent feature and draw this feature 

 together before attempting to focus the eyes. Once the views are together, an effort 

 is required to bring them into focus. This focus cannot be held more than a few 

 seconds without considerable strain. 



