818 



SIM MARY OF CURRENT RESEARCHES RELATING 10 



instance, for full-sized portraits, the perspective of a 9-in. telephoto lens, 

 with exit pupils arranged so as to come between the constituent lenses, 

 will give the perspective effect produced by an ordinary lens of 17|-in. 

 focus: or, if half-size, of a lens 14', in. This accounts for the very 



Fig. 100. 



pleasing portraits obtained by the use of the telephoto lens. For all 

 purposes, except extreme distance, the perspective foreshortening in a 

 photograph taken with a telephoto lens is less pronounced than would be 

 expected from a lens of that focal length. 



Fig. 101. 



Figs. LOO and 101 show two photographs taken, the one (fig. 100) with 

 with an ordinary photographic lens, the other (fig. 101) with the above 

 telephoto lens. Both lenses had the same equivalent focal length. The 

 object photographed was a parallel tube about 5 ft. long, built up of 

 laths covered with tissue paper. The photograph was taken 



looking 



