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 #:
000680
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. XV] DEMONSTRATING REFRACTIVE EYE DEFECTS 665 FIG. 391-392. RADIAL LINES IN BLACK AND WHITE FOR DETERMINING THE PRESENCE OF ASTIGMATISM. A lantern slide of the radial lines is very desirable for the demonstrations on astigmatism. The black lines on a white ground have the advantage that the lantern slide is less liable to break than the white lines on a black ground (ยง 852). It will be noticed that, by contrast, the central white circle seems lighter than the white spaces between the radial lines. In like manner the central black circle seems blacker than the black spaces between the radial lines. These are optical illusions, for the white is uniform and so is the black. Now place the concave cylinder in front of the convex cylinder and make their axes parallel (fig. 390). All the lines will become sharp again. This is because the concave and the convex cylinders with their axes parallel just balance each other and then act like a piece of plane glass. To compare the effect of astigmatism on printed matter with its effect on the radial lines, remove the cylinders and focus sharply the lantern slide of the history of astigmatism, (fig. 393). Now add the 0.5 diopter convex cylinder and make the axis vertical. The horizontal lines in the print will be sharp, but the others blurred (fig. 394-395). Now rotate the cylinder until its axis is horizontal, and the vertical lines will be sharp and clear (fig. 396-397). It is to be noted that with these Gothic letters, it is easier to read the words when the vertical lines are clear, because vertical lines preponderate.