Video and displays
Lens shift
An optical adjustment that moves the projected image up, down, or sideways without tilting the projector or distorting the picture.
Lens shift physically moves the lens relative to the imaging chip, so the image slides across the screen while the projector stays level. The light path stays perpendicular to the screen, so the picture keeps its rectangular shape and uses every pixel.
It gives freedom in placement: the projector can sit on a shelf above the screen or a table below it while still filling the frame squarely, which is what lets most installs avoid keystone correction entirely.
Vertical shift is quoted as a percentage of image height. A 50 percent range on a 100 inch screen (49 inch tall) lets the lens center sit up to about 24 inches above or below screen center; using horizontal shift reduces the available vertical range.
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