The book of lantern ; being a practical guide to the working of the optical (1888)

Record Details:

Title:
The book of lantern ; being a practical guide to the working of the optical
Date:
1888
Publisher:
London : Wyman & Sons
Volume:
The book of lantern ; being a practical guide to the working of the optical (or magic) lantern ; with full and precise directions for making and colouring lantern pictures
Leaf #:
00036
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Date Added:
July 19, 2022
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THE BOOK OF THE LANTERN. 2i> perfect lenses for use with the instrument. Mr. Dallmeyer thereupon determined to tackle the subject, and produced new forms of condensers and objectives, a description of which he placed before the Photographic Society. I can- not do better than quote the description of the new eon- denser from this paper, and at the same time reproduce one of the drawings shown in illustration of the remarks made (see fig. 15) :— FIG. 15. " The condenser is of 4-in. effective diameter, and 2J- in. equivalent focal length. Assuming the light to be at a safe distance of 2| in. from the flat surface of the first lens, this condenser collects an angular pencil of about 66°, i.e., about 20 per cent, more light than the shortest focus symmetrical. It consists of two unsymmetrical lenses, A and B. A is a plano-convex of flint 3|-in. diameter, and B is a double convex of crown glass of 4-in. diameter. The lenses are mounted at a certain distance apart, with their deep sides facing each other. Approxi- mate correction of chromatic aberration for centrical pencils is obtained by a proper apportioning of their focal lengths, and the distance at which they are placed. Thus : ray