International Stereoscopic Union


A Glossary of Stereoscopic Terms

accidental stereo effects

Found in fusing supposedly identical side-by-side pictures: for example, postage stamps or wall patterns, where irregularities in the printing produce a three-dimensional effect. See also false stereo effects.


The refocusing of the eyes as their vision shifts from one distance plane to another.

accommodation-convergence link (adv.)

The physiological link which causes the eyes to change focus as they change convergence, a link which has to be overcome in stereo viewing since the focus remains unchanged on the plane of the constituent flat images.

acuity (stereo)

See stereo acuity.

alignment gauge (Also "mounting grid", "mounting guide")

A positioning gauge to assist in achieving accurate placing of left and right film chips when mounting.

alternating perspective figures (adv.)

Planar drawings which jump from inside-out to outside-in during viewing.

American stereoscope (arch.)

See Holmes stereoscope.


A type of stereogram (either printed, projected or viewed on a TV or computer screen) in which the two images are superimposed but are separated, so each eye sees only the desired image, by the use of coloured filters and viewing spectacles (commonly red and cyan, or red and green).


Devices placed in front of the eyes to separate the left and right eye images, mainly when projected. Typically, these are polarising spectacles, anaglyph spectacles or liquid crystal "shutters".

aperture separation (adv.)

The distance between the centres or corresponding edges of the openings in the camera aperture plate; typically 71.25 mm in many traditional stereo cameras of 5-perforation format, or 63.5 mm in 7-perforation format.


Usually describes a stereogram designed to be viewed without the aid of special apparatus in front of the eyes (e.g. a lenticular print or a single-image random-dot stereogram.



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