Rochester Optical & Camera Co., (Rochester, NY)
Early Filters - c. 1900
3" diameter Poco
Blue Screen (dark amber), c. 1899-1903 - for eliminating all blue
rays (to simulate orthochromatic film from panchromatic film)
3" diameter Premo Ray Screen
(medium yellow), c.1903-1907 - for cloud effects
Notes:
For the first 60 years of photography, emulsions were sensitive to blue light only, one effect of which was to wash out the sky on exterior photographs. That produced brightness and contrast on the image contrary to what the eye sees - especially in sky and skin tones. With the advent and use of panchromatic (sensitive to all colors) film, the incorrect tones were somewhat improved, but still not natural.
In order to make sky and clouds in a photograph appear exactly like the eye appeared to see it, on-lens filters would be used in addition to panchromatic film.
The top filter is a Blue Screen, dark amber, which would remove all blue rays from contributing to the image. The bottom filter is a Ray Screen, medium yellow, would create a natural-appearing sky and clouds.
These filters are solid, whereas the Bausch & Lomb Ray Filter used a liquid filter medium.
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