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unsharpnessA quantitative measure of the loss of edge detail due to geometric properties of the object and imaging system and not to image noise or X-ray scatter. Unsharpness is usually expressed as the width of the band of changing density or brightness arising from a sudden change in the intensity of the radiation incident on the film or fluorescent screen.
Factors contributing to image unsharpness
Geometric unsharpness, movement unsharpness, absorption unsharpness, image receptor unsharpness and parallax unsharpness. It is known from observation that the total unsharpness is not the direct sum of the contributing factors; rather, it is dominated by the unsharpness of the largest individual factor.
lack of detail in an x-ray picture.