International Stereoscopic Union















 

A Glossary of Stereoscopic Terms

height error (or vertical error)

A fault present in a stereogram when the two film chips or prints are not aligned vertically in mounting, so that homologous points are at different heights.

Holmes stereoscope

Usual name for the common type of hand-held stereoscope with an open skeletal frame. Named after its inventor in 1859, the American physician and author, Oliver Wendell Holmes. Where, as is normally the case, the stereoscope includes a hood to shade the eyes and an adjustable card holder, it is more correctly termed a Holmes-Bates (or just Bates) stereoscope (after Joseph Bates who introduced these refinements).

holography

"whole drawing". A technique for producing an image (hologram) which conveys a sense of depth, but is not a stereogram in the usual sense of providing fixed binocular parallax information. In outline, this is accomplished by the recreation on a photographic plate of (spectrally restricted) wave fronts of light that appear as if they emanated from the subjects that were holographed, due to the recording of interference patterns between beams of coherent light scattered by the subject matter. Under certain viewing conditions, an image is obtained which is fully three-dimensional in all directions so that a movement of the head presents another aspect of the object (when in stereo viewing this would present a distortion of the same object). The production of such an image, using lasers and mirrors or prisms, is laborious and difficult and requires laboratory conditions of working.

homologues (or homologous points)

Identical features in the left and right image points of a stereo pair. The spacing between any two homologous points in a view is referred to as the separation of the two images (which varies according to the apparent distance of the points) and this can be used in determining the correct positioning of the images when mounting as a stereo pair.

hyperfocal distance

The distance setting on the focussing scale of a lens mount which will produce a sharply focussed image from infinity to half the distance of the focus setting at any specific lens aperture. Of particular value in stereo photography to ensure maximum 'depth of field', so that viewing is not confused by out-of-focus subject matter.

hyperstereo

Use of a longer than normal stereo base in order to achieve the effect of enhanced stereo depth and reduced scale of a scene; it produces an effect known as Lilliputism because of the miniaturisation of the subject matter which appears as a result. Often used in order to reveal depth discrimination in architectural and geological features. The converse of hypostereo.

hypostereo

Use of a shorter than normal stereo base in order to reduce depth distortion in portraiture and close-up stereography; it produces an effect known as Giantism (qv). The converse of hyperstereo.

 


   

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