ON THE CORRECTNESS OF PHOTOGRAPHS. 711 



it " that is, " I yn not accustomed to see such things " and it is in 

 this manner that we first discover how imperfectly we use this, the 

 most perfect of our senses. 



A man horn blind, and who receives his sight by an operation, 

 cannot at first distinguish a cube from a ball, or a cat from a dog. 

 He is not accustomed to see such things, and must first exercise his 

 eyes and learn to see. 



We, also, though in possession of sound organs, are blind to all 

 things that we are not accustomed to see ; and this fact is most ap- 

 parent in art, as also in photography, so closely related to it. 



If photographers principally engaged in taking portraits are not 

 able to produce a good landscape, the reason of this is that they have 

 no eye for landscape that they consider a picture to be good after 

 too short an exposure, or when imperfectly developed and strength- 

 ened, or when inaccurately printed. It proceeds from their not know- 

 ing the influence exercised by the position and intensity of the sun on 

 the aerial perspective produced by clouds, without speaking of other 

 points of less importance. 



Thus every class of subjects requires a special study, though the 

 manipulation of photography remains in all cases the same ; therefore, 

 there are photographers whose proper province is portraits, and others 

 devoted to landscapes, to the reproduction of oil-paintings, etc. 



The remark is frequently made by admirers of photography, that 

 this newly-invented art gives a perfectly truthful representation of 

 objects, understanding by the term truthful a perfect agreement with 

 reality. Photography can, in fact, when properly applied, produce 

 truer pictures than all other arts ; but it is not absolutely true. And, 

 as it is not so, it is important to become acquainted with the sources 

 of inaccuracy in photography. Many exist. I shall treat here es- 

 pecially of optical errors. 



A 



Fig. 1. 



The lenses which are employed in photography do not always give 

 absolutely true pictures. Suppose, for example, that a simple lens re- 

 ceives the impression of a square ; it often represents it with curvilinear 



