524 



A NOTABLE ADVANCE IN COLOR PHOTOGRAPHY. 



and then from this negative a printed ])lock is made by the usual 

 method. A second negative is made through a screen of red glass, and 

 a third through a lilue screen, plates being similarly ol^tained from 

 each. By printing the phite made through the blue glass in j^ellow 

 ink, that made through the yellow screen in a reddish ink on top of 

 it, and the third in a blue ink on top of these all the original colors are 

 produced. 



Such at least is the theor}^ and when proper pigments and exact 

 registration are employed the rcsidts are l)C3'ond criticism.^ 



As can be seen, this method is most cuni))ersome and the picture or 

 object to be reproduced must ])e taken to the engraver's gallery. The 

 exposure for the blue plate alone reipiires from live to thirty mimites 

 (a year or two ago it was frequently over an hour), and the other colors 



Fig. 1.— B (A enlarged Fig. 2.— The black and 



53 times).'- Positive on white screen used to 



glass made from origi- pick out each positive; 



nal negative; successive each black line equal in 



groups of colored lines, size to two colored lines, 

 each color repeated ev- 

 ery third line. 



Spot marked A is the exact size of a spot on the negative, of which B is 

 an enlargement. That spot is on the screen occupied by 30 colored lines in 

 exact juxtaposition, each line transmitting certain wave-lengths of light 

 in definite proportions. Screens as large as 8 x 10 have been made, ruled 

 in this fashion. 



take from thirty" seconds to three minutes additional. Of course this 

 limits one to a very restricted range of subjects. 



B}" this newly perfected process, however, onl}' one negative need 

 be made. It requires an exposure of ord}" from one-tenth to one- 

 sixtieth of a second, and the three plates into which this original is 

 subdivided are just as accurate as those made ))y the old awkward plan. 

 For the first time, therefore, photographic color prints of moving 

 objects are possible. 



What these inventors have done is to make a commercial possibility 



'As an instance of the difficulties, it may be stated that the only color known which 

 gives approximately the luminous purple-red needed is rhodamine, one of the coal- 

 tar colors; but unfortunately this fades in a few hours. So the printers have to use 

 the next best, a bluish red, which is by no means exactly right. 



