1896.] l-jl [Sachse. 



("taking ") screen. The great ditierence and the falsity of the color 

 rendering will at once be noted by comparison with the original. 



The next specimen is perhaps the most interesting one of all, on 

 account of being an almost instantaneous picture.* It represents a 

 military band in the Park of Trinity College, Dublin. It will be noted 

 that the bright reds of the uniform coats are exceptionally well ren- 

 dered. Further, this example indicates a possible application of this 

 method of color reproduction to snap-shot photography. 



I now wish to call your attention to an interesting feature of this 

 process, viz., the necessity for having the photograph and screen in 

 exact register, and viewing it in a normal position. Viewed direct, this 

 transparency shows the colors of nature : the brilliant red hue of the 

 coats is especially noticeable. Now if we turn the transparency so as 

 to view it at a slight angle, we at once note a change of the colors, and^ 

 in this particular instance, an apparent change of the nationality of the 

 subjects : in place of English soldiers in bright red coats, we see a body 

 of men dressed in brilliant green : in short, the Englishman appears to 

 have been turned into an Irishman of the most pronounced type. 



The next subject is a perfect representation of a green fluorescent 

 bowl made of uranium glass. 



We now come to another interesting specimen — a photograph of a 

 bunch of wall flowers, executed in two color sensations only, viz., the 

 red and green sensations. This picture derives an additional interest 

 from the fact that it was made by Prof Joly at the request of Lord 

 Kelvin, to show the effect of "violet blindness," an extremely rare 

 variety of color-blindness. 



I now present to your notice two pliotographs of the solar spectrum 

 from nature — the first one made through a "taking" screen, and seen 

 through a "viewing" screen, which, as you will perceive, shows some 

 of the principal lines ; the other one, both taken and viewed through 

 the "viewing " screen, shows a false color rendition. The j^ellow pass- 

 ing through the red lines only, is almost entirely represented hj pure 

 red. The incorrectness of the result is evident on comparing it with 

 the first specimen or with nature. 



I now come to the commercial part of this process. I have here for 

 your inspection a specimen of three-color printing : the original photo- 

 graph consists of a single negative ; the printing was done from three 

 separate half-tone blocks or plates — red, yellow and blue. 



This result is obtained by making three positives in the camera from 

 the original negative in the following manner : A sp<ecial screen is pre- 

 pared with black lines twice the width of those upon the taking screen, 

 the intervening space being the width of a single line. This screen, 

 when placed in register with the original negative, it will be observed, 

 exposes only every third line of the negative. Now it will be obvious 

 that if this screen be moved the width of a single line before each 



♦Actual time about three seconds. 



