Ricoh K-C3 Service Manual page 204

B245/B276/B277/B268/B269 Service Manual 18-Jan-06
Scanner Gamma Correction
The CCD output is not proportional to the quantity of light received. Scanner correction
corrects the CCD output so that grayscale data is proportional to the quantity of light
received.
The machine has two possible scanner gamma curves: Text and Photo. When selecting
Text, the machine does not use scanner gamma correction. As a result, the output is darker
than the image density on the original. The advantage of this is that the machine can bring
out gradations in paler areas. The disadvantage is that the machine cannot bring out
gradations in darker areas, i.e. differences in shades of dark colors are hard to distinguish.
When selecting Photo, the machine uses scanner gamma correction. One advantage of
this is that the machine can bring out gradations in dark areas of photo image originals. The
disadvantage is that it in some cases images come out lighter than the customer desires.
Main Scan Magnification
Changing the scanner speed enables enlargement and reduction along the sub scan
direction. However, enlargement and reduction along the main scan direction is handled by
the IPU (SCRATCH) chip. The processing for main scan enlargement/reduction is the same
as in previous digital machines.
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