Sindoh M611 - Manual (Page 126)

Scanner, Printer and Fax
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Grey Correction
You can control brightness and contrast. Through user settings you can control the brightness and control.
The default settings are Brightness(O), Contrast(-35).
Grey correction is not available for Sindoh M611_616 Series PS/PCL6.
Toner Darkness
You can adjust toner contrast level.
Toner Save
You can reduce the amount of toner for printing.