Xerox DocuMate 4799, Руководство пользователя

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Xerox
®
DocuMate
®
4799
User’s Guide
7-137
Contrast
Contrast refers to the differences between the light and dark portions in the image. Move the slider left or right to
decrease or increase the contrast levels. Increasing the contrast level emphasizes the difference between the
lighter and darker portions of the image, decreasing the contrast de-emphasizes that difference.
Choosing contrast values
While Brightness adds the same amount of gray or white to all pixels in the image, Contrast adjusts the pixels
based on the pixel color level. For instance, increasing the contrast level will add white to light colored pixels and
gray to dark pixels to make the difference between color levels in the image crisper. Decreasing the contrast level
will have the opposite affect, where light colored pixels are modified with gray and dark pixels are modified with
white to make the transition of colors in the image appear smoother.
Adjusting the contrast level is based on how you want the image to appear and there is no standard to adhere to.
Contrast works in conjunction with brightness for image enhancement, when decreasing the brightness level, the
overall image becomes darker, in which case you may want to increase the contrast level so that the differences
between the lighter and darker portions of the image are clearer.
Below are some recommended options for contrast image correction based on the original document quality.
• Original documents of good quality - 50%
• Pencil written letters, forms, or drawings - 55% to 65%
• Faded pictures or old documents with faded text - 60% to 70%
• Light colored carbon copy paper, such as yellow or pale pink or pale green, with light text - 45% to 55%
• Newspaper or magazine pages - 55% to 70%
• Book pages - 60% to 75%
• Pictures taken inside or in the shade - 40% to 60%
Color image contrast examples
The examples below show the original image at the default setting of 50% contrast level, 25% contrast and
75% contrast.
Contrast: 25% Contrast: 50% Contrast: 75%