The history of three-color photography (1925)

Record Details:

Title:
The history of three-color photography
Date:
1925
Publisher:
Boston : American Photographic Publishing Company
Volume:
The history of three-color photography
Leaf #:
000560
Language:
English
Subjects:
Motion Pictures, Motion pictures--Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
Media History Digital Library
Coordinator:
Media History Digital Library
Description:
Date Added:
September 21, 2023
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544 History of Three-Color Photography R F Fig. 141 (Page 543), Fig. 142. largement is 4 times, the projected image will be of a homogeneous red color. Under these conditions the structure of all other colors is destroyed, and Fig. 142 shows how a homogeneous yellow can be reproduced from the green and red elements g and r. In order to work out the exposure conditions under various circumstances, the numerical connection between the size of the elements in the projection, and the factors affecting the result must be known. From Fig. 139 the following equation is obtained : L *i A-m a-m and a m m calling the ratio equal to v, that is, the degree of enlargement, then a + Lm , v = and therefore m = m v-1 Substituting this value for in in the equation, we get T A (v-l)-a as a is very small in comparison with A (v-1), it can be neglected and thus we obtain the simpler equation : L = A (v-1) This tells us what must be the size of the light-source to obtain an enlargement of the element e of 4 times in the projection; A being the distance from the light-source of the original, and a its distance from the sensitive surface. In general the degree of enlargement will be so chosen that v = 4. Thus to take the example of a Dufay plate, in which the value of e is 0.1 mm., the distance of the original from the sensitive film will be 2