PHOTOGRAPHY OF AQUATIC ANIMALS. 67 



rapidly more distinct as they approach. Into them they vanish suddenly as they 

 recede. 



Subaquatic photographs show the same lack of distance that so impresses the 

 eye. Thus in the photographs shown on plate n the distance appears indistinct, 

 partly because the objects in it are out of focus, but chiefly because they are enveloped 

 in the bluish translucence mentioned above. It is therefore impossible under water 

 to photograph objects at any considerable distance. To the photographer who 

 is unfamiliar with the aspect of the subaquatic landscape this lack of distance in 

 photographs of it seems a defect. But to the artist or naturalist who has seen things 

 as they look to one beneath the water it is really a merit, since it shows these things 

 as they are. 



The source of this lack of distance is probably double. It is due in part to the 

 fact that even the clearest water contains very many bodies in suspension, living 

 organisms, and inorganic and organic particles. These, like dust in the atmosphere, 

 interfere with distance vision. It is due also in part to the reflection of the light 

 from the surface of the water. Light which has entered the water from above 

 strikes upon and illuminates various bodies beneath the surface. From these a part 

 of it is reflected to the surface of the water again. If it strikes the surface at an 

 angle of more than 48 35' with the vertical it is totally reflected and passes again 

 into the water. Here it again strikes some submerged body and is again in part 

 reflected to the surface and here again in part re-reflected- Thus shallow water is 

 traversed in every direction by beams of light which intercross at every angle. 

 These illuminate the opaque particles floating in the water and are deflected bv 

 reflection. They are also deflected by refraction through the more transparent 

 organisms. In this way probably is produced the background of bluish-white 

 opalescence which characterizes the subaquatic landscape. To one who knows 

 that landscape, the background, hiding many mysteries, adds to it character and 

 beauty. A photograph that failed to show it would be lacking in character. Boutan 

 (1893), who discusses this subject, made use of a blue color screen and believed that 

 he obtained greater distance in his subaquatic pictures by this means. In his more 

 recent work (1900, p. 283) he abandoned the use of the color screen. He obtained 

 clear pictures of near objects by using a shade above the lens, as already described. 

 Boutan appears never to have obtained clear pictures of more distant objects. The 

 writer has made use of an ordinary yellow color screen (graphic no. 3) but is unable 

 to say with certainty that it adds anything to the distance in his pictures. The 

 subject needs further study. 



A second characteristic of the subaquatic photographs that strikes the photog- 

 raphers unpleasantly is their flatness. Objects of all sorts appear lacking in thick- 

 ness or rotundity and do not cast abrupt or heavy shadows. This peculiarity the 

 writer believes to be due to the reflection of light from submerged objects into the 

 water at the water's surface. Light thus reflected on the subaquatic object from 

 the bottom beneath and from the surface above and at all angles takes out of it 

 much of its roundness. It takes out the shadows very much as a photographer in 

 his studio may take them out by a suitable adjustment of reflecting screens. Along 

 with this flatness of the individual objects in the subaquatic photograph there is 

 abundance of contrast between different parts, as may be seen in plate I. 



