19li 



NATURE-STUDY REVIEW [12:5— May, 1916 



he may exclaim, "What a lovely view," and proceed to make the 

 exposure at once — if the light is favorable. 



Ray Filters 



Whenever greens, yellows, oranges or red are a prominent part 

 of the subject to be photographed (whether it be a close study 

 or a landscape), or where sand, water or clouds form a conspicuous 

 part of the landscape on a very bright day, the use of a ray filter 



Fig. 2. "Blow-out." Note the open center. 

 Dune Park, Ind., March, 1915. Aperture F-32, time 30 seconds, diffused light. 



in front of the lens will add greatly to the correctness of the 

 values in the picture. 



White or natural light is a mixture of red, orange, yellow, green 

 blue and violet rays. Until recently, the plates in general use 

 were sensitive to only the blue and violet rays, and the red, orange 

 and yellow objects "took as black;" since green is a "mixed" 

 color, the greens took as black or white, depending on the propor- 

 tion of yellow to blue in the particular shade. The plates now in 

 use for out-of-door work are sensitive to all the primary colors 

 except red, and are variously known as "isochromatic," or "ortho- 



