acutance

Definition: (1) In photography: the density gradient across an edge separating light from darkness. * This can be measured with a micro-densitometer and correlates with subjective assessment of sharpness or definition: a sharp gradient i.e. rapid change equates with higher sharpness. (2) In machine vision, a measure of the sharpness of edges in an image: equals the average squared rate of change of density across the edge divided by the total density difference from one side of the edge to the other.

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