STEREOSCOPIC PROJECTION IN NATURAL COLORS. 
BY C. F. LORENZ. 
The projection of pictures on a screen in such a way 
that they shall show relief, like that given by a stereoscope, 
has been accomplished by two methods, one of which de- 
pends on the use of polarized light, and the other on the 
use of color-filters. The following is an account of a 
modification of the latter method, which enables us to see 
the projected picture in relief, and at the same time in the 
original colors. A signal lantern is used. 
As is well known, to make a natural-color lantern slide 
by the method of three superposed positives, three negatives 
are taken from the same point of view, through red, green 
and blue-violet color screens respectively ; from these are 
made positives which are colored in the shadows and clear 
in the high-lights, the one from the red-record negative 
being cyan-blue, that from the green-record negative 
being magenta red or “pink,” and that from the blue-violet 
record negative being yellow. Now let one of these nega- 
tives, say the green-record, be taken from a slightly 
different point of view; the pink print will then not 
register with the other two, and the resulting picture will 
be blurred. But w 7 hen the screen is viewed through a 
pink glass over one eye and a green glass over the other, 
then the picture will stand out in relief, provided that the 
pink and green glasses are held respectively over the 
proper eye, because the pink picture will be invisible to 
the eye covered with the pink glass, while the picture 
formed by the combination of the yellow and the cyan- 
blue prints will appear to this eye as a picture black in the 
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