Proceedings PaperAcutance And Granulance
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"Acutance," an established concept, is an objective prediction of picture sharpness, which is subjective. "AMT acutance" is 100 + 66 log R, where R is the ratio of the area under the modulation transfer curve of a complete imaging system including a human eye to that under the eye curve alone, which is Gaussian with standard deviation 13 cycles per degree. AMT acutance 100 is excellent, 90 is good, 80 fair, and 70 just passable. We propose a new measure of acceptability so far as noise is concerned, on the same scale, to be called "granulance." It is based on the rms deviation, in 240-μm circular samples, from mean lightness in areas meant to be uniform. A tentative formula for granulance of a paper print is: minimum value of 100 - 40 log [650 x rmsL(film) x scene lightness x slope of the curve of paper lightness vs. scene lightness].