The advance of photography : its history and modern applications (1911)

Record Details:

Title:
The advance of photography : its history and modern applications
Date:
1911
Publisher:
London : K. Paul, Trench, Trübner & Co., Ltd.
Volume:
The advance of photography : its history and modern applications
Leaf #:
000148
Language:
English
Subjects:
Motion Pictures, Motion pictures--Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
Media History Digital Library
Coordinator:
Media History Digital Library
Description:
Date Added:
November 02, 2023
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124 THE ADVANCE OF PHOTOGRAPHY certainly very fine results can be obtained with lenses of this type. The construction of this lens is shown in the accompanying diagram (39). Portrait Lenses. — The lenses required for portraiture are of much more rapid action, and the great bulk of these are still of the ordinary or Petzval construction. These lenses give a soft definition over a small area, and in some the back combination consists of two lenses, the distance between which can be altered by unscrewing the back. When screwed up tight, the definition is at its best, and a softening of definition is produced by slightly unscrewing. The diagram shows a very rapid type of portrait lens which works at an aperture f/2'24. Such a lens is especially useful in the photography of small children. The softening of the definition of the image produces such fine results in portraiture that a special lens has been invented which enables this kind of work to be carried out with the least possible amount of inconvenience. When an object is put out of focus with an ordinary lens, the form of the object is also to some extent altered, but this new lens gives diffusion of focus without in any way diminishing the beauty of the form. It is known as the Dallmeyer-Bergheim lens, and, as can be seen from the diagram, it consists of two simple lenses, the front one positive (converging), and the back negative Fig. 40.