parallax

Definition: Apparent change in size or position of image with change in viewpoint or other factor. * (1) Monocular ~: the relative shift in position between two objects with change in position of viewing. * This is the most common experienced and is seen e.g. when comparing the image seen through the viewfinder of a direct-vision camera and the image taken by the lens. (2) Binocular ~: difference in angle subtended at the eye by an object when viewed with one eye, then the other: apparent when e.g. a box is viewed close up: one eye may side one side of the box that is hidden to the other. (3) Time ~: change in position of moving object between moment that exposure is initiated and when photograph is actually taken. Also known as shutter-lag. (4) Chromatic ~: apparent shift in position of e.g. red and blue objects when viewed in certain controlled conditions. when the eyepoint is moved laterally. When parallax appears in a telescope between the image and reticle, this indicates the image has not been formed in the plane of the reticle.

Previous Term: paraboloidal condenser  Next Term: parallax correction