About GammaCorrection5-5Additional Technical InformationThe following illustration shows the relationship between screen fre-quency, gray levels, and print resolution. As the screen frequencyincreases, the number of gray levels decreases.The number of gray levels that your printer can produce depends onthe screen frequency and the print resolution. The default value forscreen frequency using 600 dpi is 71 lpi. This typically allows 73 dif-ferent levels of gray. The default value for screen frequency using 300dpi is 53 lpi. This typically allows 33 different levels of gray.You can change screen frequency through your application or byusing the PostScript setscreen operator. TheQMS Crown TechnicalReference Manual contains information on setscreen.The extra gray levels available through higher resolution provide asmoother shift from the darkest black to very light grays while higherresolution provides sharper image outlines.Gamma Correction ConceptOften in scanned images, gray scaling may be too light or dark toshow details clearly. Using gamma correction on a gray-scale imageis similar to using a graphic equalizer on a home stereo; the range ofgray levels is adjusted for the best possible image. This sharpens300x300 dpi600x600 dpi42 53 71 106Screen Frequency (lpi)Gray Levels2502001501005005133 19 92011297333
