TELEPHOTO LENSES 141 



The increased simplicity in illumination obtained by 

 the longer object distance is obvious ; and in the case of 

 larger magnifications the difference in camera extension 

 is very considerable. 



The lens separation required in the above cases varies 

 from about 5" to 11"; a small change in separation is 

 equivalent in its effect on magnification to a rather large 

 change in camera extension, and in consequence it is 

 simpler to obtain final focus by adjustment of the lens 

 after the camera extension and magnification have been 

 roughly fixed. 



