Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration (1906)

Page scan 00016 from Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration

Record Details:

Title:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Date:
1906
Author:
Wright, Lewis, 1838-1905
Publisher:
London, New York, Bombay : Longmans, Green and Co.
Volume:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Leaf #:
00016
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
Date Added:
July 19, 2022
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OPTICAL PEOJEGTION CHAPTER I ON PROJECTION 1. Definition.—Projection, in the optical sense and in this book, is the production of a picture or image—usually a magnified image—upon some kind of screen or visible plane, generally by means of a lens. The image may be that of a picture, or of some solid object or piece of apparatus. It is manifest that the excellence of the projection—that is, the brightness and distinctness of the picture on the screen— must depend upon many practical conditions, which are to be treated of in these pages. But first of all it is essential that the nature of the problem itself be really understood, if the best result is to be obtained with the apparatus at our disposal. 2. Image not formed by the Lens.—The reader would probably gather from most of the treatises upon optics, that the image on the screen which he has to produce is formed by the lens; but that is not true, except in a very secondary sense. The first and cardinal truth for an intelligently successful demonstrator to grasp, is the fact that all power of really forming' an image resides in those rays of light themselves by which any object is visible to us. Starting with, and here taking for granted without need-