International Stereoscopic Union


A Glossary of Stereoscopic Terms

Savoy format (adv.)

A stereo format produced by prisms or other forms of image-splitter on a planar camera, side-by-side for still images and over-and-under for cine images.

separation (interaxial)

The distance between two taking positions in a stereo photograph.

Sometimes used to denote the distance between two homologues.


The partition used in a stereo camera to separate the two image paths.

Any partition or design element that effectively separates the lines of sight of the eyes such that only their respective left and right images are seen by each one.

sequential stereograph

A stereo pair of images made with one camera which is moved by an appropriate separation between the making of the LH and the RH exposures.

siamese (coll.)

Used as a verb, to assemble a stereo camera from the relevant parts of two similar planar cameras. Therefore, siamesed (adjective) to describe the finished assembly.

single-image random dot stereogram (SIRDS)

A form of random dot stereogram in which the stereo pair is encoded into a single composite image which each eye has to decipher separately. Popularised in the 'Magic Eye' type books of the 1990s.

slide bar

A device for taking sequential stereo pairs of non-moving subjects, enabling a planar camera to move by an appropriate separation (qv) whilst holding the camera in correct horizontal register with the optical axes either parallel or 'toed-in' to create a convenient stereo window.

squeeze (coll.)

Diminution of depth in a stereogram in relation to the other two dimensions, usually resulting from a viewing distance closer than the optimum (especially in projection). The opposite effect to stretch.

stereo- [from Greek stereos, = 'solid']

Having depth, or three-dimensional: used as a prefix to describe, or (coll.) as a contraction to refer to, various stereographic or stereoscopic artefacts or phenomena.

stereo acuity

The ability to distinguish different planes of depth, measured by the smallest angular differences of parallax that can be resolved binocularly.

stereo infinity

The farthest distance at which spatial depth effects are normally discernible, usually regarded as 200 metres for practical purposes.

stereo window

The viewing frame or border of a stereo pair, defining a spatial plane through which the three-dimensional image can be seen beyond (or, for a special effect, 'coming through').

A design feature in some stereo cameras whereby the axes of the lenses are offset slightly inwards from the axes of the film apertures, so as to create a self-determining window in the resulting images which is usually set at around an apparent 2 metres distance from the viewer. (See toeing-in.)


A general term for any arrangement of LH and RH views which produces a three-dimensional result, which may consist of
(1) a side-by-side or over-and-under pair of images,
(2) superimposed images projected onto a screen,
(3) a colour-coded composite (anaglyph),
(4) lenticular images,
(5) a vectograph or
(6) in film or video, alternate projected LH and RH images which fuse by means of the persistence of vision.


The original term, coined by Wheatstone, for a three-dimensional image produced by drawing; now denoting any image viewed from a stereogram.

In more general but erroneous usage as the equivalent of stereogram.


An early type of stereoscope which also carries a large monocular lens (above the two regular stereoscopic lenses) for the viewing of planar photographs.


A person who makes stereo pictures.


The art and practice of three-dimensional image making.


The physiological and mental process of converting the individual LH and RH images seen by the eyes into the sensation and awareness of depth in a single three-dimensional concept (or Cyclopean image).

stereopticon (arch.)

Term sometimes (erroneously) used to describe a stereoscope. First used (1875) to identify a dissolving twin-image magic lantern which could be used to convey information about depth by the blended sequential presentation of a series of planar views of a subject; later applied to some other kinds of non-stereo projectors.


A device for viewing stereograms, employing prisms, lenses or mirrors to facilitate vision and the fusion of images.


'Solid looking': having visible depth as well as height and width. May refer to any experience or device that is associated with binocular depth perception.


The reproduction of the effects of binocular vision by photographic or other graphic means.


stretch (coll.)

The elongation of depth in a stereogram in relation to the other two dimensions, usually caused by viewing from more than the optimum distance, especially in projection. The opposite effect to squeeze.



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