a stereo/photo glossary - phsc.ca

title-and-maker description characteristically provided on the face of the card. ...... issue of Stereo Views, newsletter of the Cascade Stereoscopic Club.) * The text ...
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A Stereo/Photo Glossary

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A STEREO/PHOTO GLOSSARY (Second edition, version 93.5/97.4a) by: Craig Daniels and Dr. Dale E. Hammerschmidt

This short work is intended for anyone interested in stereoscopic pursuits, but particularly for those who are trying to create stereoscopic images. We hope that the words and phrases to be found here will become useful tools rather than obstacles in your approach to "3-D" imaging. We stress that this is a compendium of terms that we have found useful, confusing and/or interesting; while we have tried to make it accurate, we do not represent that it is complete or of great scholarly depth. Some entries are long, because we found the subject interesting or we knew a lot about it; some are short for the obvious other reasons! We have tried to keep the tone conversational, rather than strive for uniform and rigid style; we've not felt ourselves above an occasional wise-crack. Additions, corrections and improvements are always welcome --- we see ourselves as editors rather than authors. (Glossary is available via diskette or e-mail.) * ANSI: American National Standards Institute. See next entry. * ASA: (1) American Standards Association. Although the expression "ASA" is still applied to U.S. film speeds, the "American Standards Association" changed its name to the "American National Standards Institute" in 1969. Their standards are referenced by ANSI numbers such as "PH3.11-1953" (which describes the 5p format used in cameras like the Stereo Realist and the Kodak Stereo 35). (2) As a film speed, it now appears in conjunction with the European DIN number (see) in the format "100/21"" which, as such, is the "ISO" speed. Relative film speed is proportional to the ASA value. Absolute film speed is determined by a formula which in turn describes the judgement of a panel of experts who have been shown the results of carefully controlled trial exposures. If you don't like the results of using the prescribed speed, use another and term it your "EI" or "exposure index. Photographers often prefer to use higher EIs for transparency films (to prevent color wash-out) and lower EIs for negative films (to ensure adequate negative density). * Accessory lens(es): Lenses that --as with planar cameras-- enable the stereo camera to focus and/or converge closer (see: "Angle lenses"). Close-up lenses allow close focusing without the complications of excessive lens extension, need for exposure compensation, and the like. Other accessory lenses include those which alter the angle of acceptance, producing in effect modest wide-angle or telephoto effects. * Accidental Stereo Effects: Those stereo effects encountered by --for example-- fusing two postage stamps with printing irregularities or encountering a pair of photographs in which there has been incidental lateral displacement between the two exposures. Sometimes called a "found stereo" by analogy to that venerable genre, the "found poem." * Accommodation: The refocusing of the eyes as their vision shifts from one distance to another. When using a stereoscope or "free-viewing", accommodation is uncoupled from "convergence"; those two processes are normally linked to one another as a reflex. * Achromatic (lens): Lenses designed to avoid chromatic aberration. Simple oneelement lenses and prisms, when focusing rays of "white" light can't bring the rays to



A Stereo/Photo Glossary

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a single point (or image made up of points). Instead, a family of images (a blur) consisting of differently colored versions of the image/point(s) are created.

(1)(VL-3) An achromat brings the main colors contained in white light to a common sharp focus. This is achieved by having two or more lens elements, which differ in shape and/or refractive index, such that their chromatic aberrations tend to cancel each other out. For example, a mildly diverging (minifying; minus-diopter) lens of high refractive index ma