Identifier: americanannualof1892newy (find matches)
Title: The American annual of photography
Year: 1892 (1890s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University

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all. It may be said to hold the same relation to timethat a mathematical point holds to a line. It is a point intime, but not a portion of time. An instantaneous exposurethen is no exposure at all. This may seem a little para-doxical, but that is because our ordinary use of the wordinstantaneous is inaccurate. Strictly speaking, there can be nosuch thing as an instantaneous exposure. Every exposuretakes time. It may be only a hundreth, or perhaps only a thou-sandth of a second; but if it were only a millionth of a secondit would still be time, and immeasurably more than an instant. The so-called instantaneous exposures differ very greatlyfrom each other in duration. One operator snaps the shutterand makes an exposure in one-tenth of a second. Anotheroperator snaps the shutter and makes an exposure in one-hundredth of a second. In comparing notes, they treat theseexposures as if they were just alike, because they call themboth instantaneous; but in fact the one is ten times as long as
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J. E. Line, Photo. BYE, BYE, PAPA. Electro Tint Eng. Co., Phila. AND PHOTOGRAPHIC TIMES ALMANAC. 135 the other just as truly as if the one had been a minute and theother six seconds. It may be easy to tell the difference between one-tenth andone-hundreth of a second, by the eye or the ear; but it is im-possible to distinguish between one-fiftieth and one two-hundredth of a second by these senses. We ought to havemore accurate methods of measuring these very short intervalsof time. By the use of such methods we would attain twovery desirable ends. We would make our exposures morenearly as they should be, and, knowing the time of exposure,we would develop our negatives more intelligently. Fortunately for the development, our errors in time arelikely to be nearly all in one direction. We are not likely tomake an over-exposure with a snap-shutter. The thing weare likely to do is to make the exposure too short—even shorterthan necessary. For example, we wish to expose a plate ona steambo

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