PROGRESS IN COLOR PHOTOGRAPHY. 



By G. H. NlEWENGLOWSKI. 



Color photography is the order of the day. Within the last year 

 there have been numerous exhibitions of color photographs, one of the 

 most notable of which is that recently established on the boulevard des 

 Italiens by the brothers Lumiere of Lyous. The time is therefore 

 appropriate to give a brief review and comparison of the various proc 

 esses of photographic reproduction in colors which have thus far been 

 proposed. 



Methods of color photography may be either direct or indirect. The 

 first class contains those which give at a single direct operation a proof 

 in colors. 



Many of the direct processes are variations of the method called the 

 destruction of colors, originated by Charles Cros, and described by him 

 as follows in the Moniteur de la Photographie (1881, p. 67) under the 

 title of direct polychromy : 



"The fundamental experiment upon which polychromy is founded is 

 this: 



"A glass plate is coated first with collodion dyed red with cartha- 

 niine. To this is added a second coat of gelatine dyed blue with 

 phyllocyanine, and finally a coat of collodion dyed yellow with tumeric. 



" Upon subjecting this plate to an image formed in green, yellow, 

 and orange light the following occurs: 



"The green light produces no appreciable effect upon the yellow and 

 blue coatings, but is absorbed in the red coating and decolorizes the 

 carthamine. Thus there remains only yellow and blue at this point in 

 the coatings of the glass plate, and these two colors superposed pro- 

 duce green. Hence the green light leaves a green trace. 



"Similarly, violet light destroys the yellow, and leaving blue and red 

 superposed gives a violet trace, while the orange light, destroying the 

 blue, leaves only yellow and red, which superposed give orange. 



"Finally white light destroys all these pigments aud leaves only the 

 colorless plate, while in the absence of light none of the pigments are 

 affected and there remains the neutral tint formed by the superposition 

 of all three. 



"Thus the resulting effect is a direct positive transparency repro- 

 ducing the original colors. But this positive is not durable, for under 

 the action of light it disappears." 



1 Translated from Cosmos, Paris, 1899. New series No. 741, pp. 433-437. 

 SM 98 14 209 



