Gestetner G060 Service Manual page 647

Printer Gamma Correction
Fig. 1
G570D989.WMF
Ideally, the gamma curves for Yellow, Magenta, Cyan, and Black should be
identical, as shown in figure 1. However, slight variations in the electrical
components can result in varying gamma curves, as shown in figure 2.
• Printer characteristics are much more variable than the scanner. Printer gamma
needs recalibration and adjustment from time to time.
• The Auto Color Calibration (ACC) procedure compensates for any discrepancies
in color reproduction.
• ACC makes new gamma curves for each color in each mode (text, photo, and
black text).
• After ACC, the gamma curve for each color can be adjusted with service
programs (SP4-909 to SP4-918).
• 4 different modes:
1) ID max.
2) Shadow (High ID)
3) Middle (Middle ID)
4) Highlight (Low ID)
• If the previous gamma curve was better, it can be recalled.
• Factory settings can be loaded using SP 5-610-4.
NOTE: If the factory settings have been overwritten, this will return the new
values, not the actual settings made in the factory. This is deliberate,
since some drift is expected. After a time, the original factory settings
may no longer be suitable.
• Factory settings can be overwritten by the current gamma settings using SP5-
610-5.
SM 6-15
IMAGE PROCESSING
K
Fig. 2
G570D990.WMF
G570