IBM 1725 SLS - Manual (Page 132)

Using Gamma
Correction
QMS 1725 SLS Print System User's Guide 4-6
Gamma Correction Concept
Often in scanned images, gray scaling may be too light or dark to
show details clearly. Using gamma correction on a gray-scale image
is similar to using a graphic equalizer on a home stereo; the range of
gray levels is adjusted for the best possible image. This sharpens
overall midrange contrast while blacks (shadows) and whites (high-
lights) keep their original values. Gamma correction sets grayscale
values specified through the PostScript setgray operator to your
printer’s gray-scale values.
Gamma correction is linked to print resolution. The main benefit of
gamma correction is that it improves the print quality of a scanned
image by improving halftones at a given resolution. To get the best
gray-scale PostScript image at any resolution, gamma correction
should be turned on.
You can set gamma correction through PS Exec or through the
Administration/Engine/Gamma Correction menu.
Menu Administration/Engine/Gamma Correction
Choices 0, 1, 2, 3
Default 0
Notes 0— the gamma correction is turned off.
1—gamma correction provides a low contrast.
2—gamma correction provides medium contrast
3—gamma correction provides a high contrast
Gamma correction applies only to PostScript images.
If turning on gamma correction doesn’t yield a suitable gray-
scale image for your needs, set a specific gamma correction
value through your drawing application or through the
PostScript settransfer operator. (See your drawing application
documentation and the PostScript Language Reference
Manual for more information.)