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 #:
000482
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
Something wrong or inaccurate about this page? Let us Know!

Thanks for helping us continually improve the quality of the Lantern search engine for all of our users! We have millions of scanned pages, so user reports are incredibly helpful for us to identify places where we can improve and update the metadata.

Please describe the issue below, and click "Submit" to send your comments to our team! If you'd prefer, you can also send us an email to mhdl@commarts.wisc.edu with your comments.




We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.

Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.

CH. XII] SIZE OF SCREENS 467 If the lantern cannot be at the back of the room, but must be closer to the screen, then the projection objective must be of shorter focus than 25 to 30 cm. (10-12 in.). To determine the proper objective to use to give the desired size of image in any case one must proceed as follows : 1 i ) The size of screen image is decided on by remembering that it should be between one-fourth and one-fifth the distance to the farthest seat in the room. (2) The distance from the screen to the lantern must be measured. (3) Following the simple optical law founded on the geometry of similar triangles that: "The size of object and image vary directly as their distance from the center of the objective," one can by simple proportion get the focus which the objective should have for a given screen image. § 637. Examples. — For example, suppose the distance from the screen to the farthest seat is 20 meters (66 ft.), the width of the screen should be not less than one-fourth this distance, i. e., five meters (16.5 ft.). Now suppose that instead of the lantern being 20 meters from the screen it is only n meters (36 ft.) from it, what should be the focus of the projection objective to give a screen image 5 meters (16.5 ft.) wide? The formula best adapted for this calculation is: f d where f is the distance of the object from the center of the objective (focus of the objective). 0 is the size of the object. d is the distance from the objective to the screen. 1 is the size of the screen image. It is assumed in all the calculations for the magic lantern that the width of the lantern-slide opening or picture is 7.5 cm. or 3 inches.