File:The American annual of photography (1922) (14781766615).jpg

Identifier: americanannualof36newy (find matches)
Title: The American annual of photography
Year: 1922 (1920s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University

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son that they have given results with him in theparticular work for which he wished to use them. Lenses. A lens, good, bad, or indifferent, some one has said,is worth just about what you paid for it. A high priced lensfor photographic work like a good microscope objective meansgood workmanship, and is backed by the advertising, and bythe reputation of a reliable firm. There is, however, onefactor that adds greatly to the price of many of the lensesknown as anastigmats. This is what is known as speed.The aim of the modern lens maker is to produce a lens thatwill work at very short exposures in poor light, or will catchrapidly moving objects in good light. This means that thelens has a large aperture, and large aperture lenses do nothave depth of focus; it is optically impossible to have bothat the same time. But the biologist does not need speed one time in a thou-sand. So, unless the laboratory lens is to be used surrepti-tiously for pictures of the baby at home, or of auto races, 256
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uo 14-1v 6 pi) CO O < QO < its wide aperture and resultant speed is useless. A rectilinearwill, in most cases, do just as well as a high priced anastigmatsince they will both have to be stopped down to a smallaperture to secure depth of focus, and at these small openingsthe results obtained could not be distinguished even by anexpert. A lens of the speed known as F/6.8 will answerall requirements. Fine definition and a brilliant image arethe real measure of a lens for scientific purposes. The authoris strongly prejudiced in favor of the cemented type of lens,and has used a Voigtlander Collinear Series III and a B. &L. Plastigmat for years with better success than with theair space lenses. Nearly all, if not all, of the cheap anastig-mats are of the latter construction. The advantage of thecemented lenses is that they work against the sunlight with-out flare and give a brilliant image. A lens of as short afocal length as possible is of advantage in giving depth offocus. A sev

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