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 #:
000241
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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226 MICRO-PROJECTION FOR LARGE CLASSES [Cn. IX objective with larger lenses admits much more light, hence the screen image will be brighter. For example, suppose it were desired to obtain the magnification which is given by a 2 mm. objective, it would be much better to use a 4 mm. objective and an amplifier doubling the size of the real image. This would make the screen image of the same magnification as the 2 mm. would give, and it would be far brighter and show a larger field. In like manner and for the same reason, it is better to use an 8 mm. objective and an amplifier, than a 4 mm. objective without the amplifier (but see ยง 401). A B C D FIG. 124. FIGURES SHOWING THE GENERAL CONSTRUCTION OF MICROSCOPE OBJECTIVES. A Low power objective of a single combination (50-30 mm. equivalent focus). B, C Medium power objectives with two combinations (25-12 mm. equivalent focus). Sometimes the front combination is composed of two and sometimes of three lenses as shown. D High power objective (8 to 2 mm. equivalent focus). Usually the front combination is of a single lens, the others of two or three lenses as shown. Many high power objectives have but three combinations. (D is from Voigtlander's Catalogue). The writers have found that in projection for actual class demonstrations, objectives of higher power than 4 mm. arc unsatisfactory. We believe also that the purpose of class-room projection is not the demonstration and study of minute details which require that the observer should be close to the screen image, but the general outlines and broad features which can be seen clearly at a distance when suitably magnified.