Definition: (1) For input devices e.g. cameras, scanners: measure of the ability of a system to reproduce details present in a subject so that they are in the image. * Measure of highest spatial frequency which can be recorded by the system. * Units: total number of usable pixels for digital cameras; points per inch for scanners; line pairs per millimetre for objectives (do not confuse with lines per inch). (2) For output devices e.g. printers, film-writers: measure of system's ability to address or refer to separate points or lines of output. * Units: dots per inch. (3) Measure of system's ability to distinguish variations in colours or of density. * Units: bit depth (total number of bits available for encoding values). (4) For positioning or focusing mechanisms: the minimum repeatable adjustment increment achievable.

Related Terms: bit depth, lpi

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