Ricoh B245-62 Service Training page 37

Scanner Gamma Correction
Scanner gamma correction brings out gradations in darker
areas.
Scanner gamma correction is used in photo mode only.
Slide 37
The CCD output is not proportional to the quantity of light received. Scanner gamma
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.
Text
Original
density
37
Photo
Output density
B245-62 / PD-C4