The American annual of photography (1912) (14579266767)

Identifier: americanannualof1912newy (find matches)
Title: The American annual of photography
Year: 1912 (1910s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University



Text Appearing Before Image:
for the reason that under someconditions the ratio of exposures may be possibly six timesnormal exposure for the violet, twelve for the green and fifteenfor the red. Other times the ratio may be quite different.This complicates the problem to such an extent that very littlereally successful three-color work is done from nature. The other and much simpler method is based on the samethree-color principle, but the color filters, red, green and violet,are printed on the plate itself in very minute particles, theidea of the fine particles being to get them invisible to the eye.This is accomplished in the Lumiere autochrome plate by dye-ing potato starch grains in each of the three colors and thenmixing them until they form a neutral gray. They are thendusted on a glass plate that has been coated with a tackyvarnish, to which they adhere, thus forming a composite filterthat to the eye looks gray. The emulsion is then coated overthis composite filter, and the exposure is made through the 30
Text Appearing After Image:
A CUP OF TEA. J. WILL PALMER glass side, so as to have the light pass through the color par-ticles before reaching the emulsion. These minute filters actjust the same as the large filters in regular three-color work.The great difference in the two methods is that prints on paperare made in red, yellow and blue, whereas those by the screen-plate method use red, green and violet. There are no yellowsor blues, but the mixture of red and green produces yellow,and the mixture of green and violet makes blue. This method, to my mind, is the process that is the mostpromising, for the reason that all the pictures being on oneplate the gradation must be the same. The ratio of exposures is 31 obtained by using a filter at the lens that dampens down thosecolors that act too rapidly so that all three act at exactly thesame speed. On the autochrome plate the starch grains arenot perfectly transparent, and also the spaces between thegrains are filled in with black. All together so much light isabsor