Optic projection : principles, installation and use of the magic lantern, projection microscope, reflecting lantern, moving picture machine, fully illustrated with plates and with over 400 text-figures (1914)

Record Details:

Title:
Optic projection : principles, installation and use of the magic lantern, projection microscope, reflecting lantern, moving picture machine, fully illustrated with plates and with over 400 text-figures
Date:
1914
Author:
Gage, Simon Henry, 1851-1946
Publisher:
Ithaca, N.Y. : Comstock Publishing Co.
Volume:
Optic projection : principles, installation and use of the magic lantern, projection microscope, reflecting lantern, moving picture machine, fully illustrated with plates and with over 400 text-figures
Leaf #:
000485
Language:
English
Format:
Books
Contributor:
Gerstein - University of Toronto
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
Bibliography: p. 693-703
Date Added:
July 19, 2022
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47° SIZE OF SCREENS [Cn. XII In this example f is unknown, (i. e., the focus of the objective). 0 the height of the object is 7 cm. (2^4 in.). d the distance of the screen is 14.3 meters (47 ft.). 1 the size of the image is 2.9 meters (9.5 ft.). Substituting the values in the formula we have : For metric values : — or f = — -^ = 34.5 cm., focus of the objective. 7 2.9 2.9 For English values : or f = -^ = 1 3. 6 in., focus of the objective. 2-75 9-5 9-5 An objective of 13.6 in. or 34.5 cm. would have to be specially constructed. Those on the market and easily procurable were of 30 cm. (12 in.) and 38 cm. (15 in.). The shorter focus objective gave considerably too large a screen image and could not be used, therefore the one of longer focus was taken, and a correspondingly long focus condensing lens used. Second example. In another lecture room the lantern must be 16.75 meters from the screen and the screen could not exceed 3.35 meters in width, what should be the focus of the objective and the second element of the condenser to meet these conditions? Applying the formula : = — '-^ whence f = 37.5 cm. the focus of the objective needed. 7-5 3-35 In English measure : = -— whence f = 1 5 in. That is, a 1 5 inch objective is demanded. 3 ii § 640. Size of screen and screen images for micro-projection. —Here the law holds, that to be satisfactory, the details to be shown must be large enough so that they can be seen with ease. The microscopic specimens vary so greatly in character that no