PHOTOGRAPHY IN THE COLORS OF NATURE. 155 



amounts to the same thing, ami would not obviate the defect I have 

 mentioned as resulting from the doubling of intensity on uncolored 

 objects. Heproposed to make one negative through an "orange" screen, 

 calculated to absorb the blue light and transmit the red and yellow; 

 one through a "violet" screen, calculated to absorb the yellow light and 

 transmit the blue and red; one through a "green" screen, calculated 

 to absorb the red light and transmit the yellow and blue. 



It was no more possible to carry out this idea in Duhauron's way in 

 1808, than to carry it out in Collen's way in 1805. It is true, Duhauron 

 tried to carry it out, and showed, specimens of work, but the red and 

 yellow rays did not act on his sensitive plates,* and he admitted, in a 

 communication to the French Photographic Society,! that ''the pro- 

 duction of good results will - - - involve the manufacture of com- 

 pounds which have not yet been created." 



Soon after Duhauron showed his lirst specimens, Charles Cros, of 

 Paris, published another modification of Collen's plau.| I^ike Collen, 

 Cros proposed to make one negative by the action of red light, one by 

 yellow, and one by blue, but by exposing the sensitive plates through 

 red, yellow, and blue screens instead of employing plates sensitive to 

 single colors only. Instead of superposing each pair of these nega- 

 tives to make each color print, he proposed to make a green print 

 from the negative made by red light, a violet print from the negative 

 made by yellow light, and an orange print from the negative made by 

 the blue light. He also suggested that ordinary positive prints made 

 from these negatives might be illuminated each by the kind of light 

 which it represented, and the three combined by the aid of suitable 

 optical devices so as to form a single picture, showing all the colors. 

 Cros's plan, although it could not succeed, because based upon the 

 same false and misleading theory as that accepted by Collen and 

 Duhauron, nevertheless possessed one important advantage over the 

 preceding methods: it was free from the defect of doubling intensity on 

 those parts of the negatives representing pale or uncolored objects. 

 But this advantage would be lost again in the production of green, 

 violet, and orange colored prints, which will combine to reproduce 

 yellows and blues only with a degree of degradation comparable to 

 that produced by Duhauron's method. 



On December 3, 1809, M. Poiree, of Paris, in a communication to the 

 Photographic Society of France, § expressed doubts concerning the cor- 

 rectness of Duhauron's and Cros's theories, and suggested that better 

 results might be had by making a greater number of negatives — a sep- 

 arate negative for each spectrum region. He said, " The process which 

 seems likelj^ to succeed best is that in which the colors are analyzed by 



* Yellow ]>iyments were photographed by the green rays which they reflected. 



t rhoto(/rapMc News, 1869, p. 319. 



J Described iu rhotofji-aphic News, October 8, 1869, p. 483. 



§ The British Journal of Phoiofp-aphy, 1870, p. 26. 



