Optical format

Optical format is a hypothetical measurement approximately 50% larger than the true diagonal size of a solid-state photo sensor. The use of the optical format means that a lens used with a particular size sensor will have approximately the same angle of view as if it were to be used with an equivalent-sized video camera tube. In a video camera tube, the diagonal of the actual light-sensitive target was about two-thirds the outside diameter, which was the measure used.

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