Canon CANOSCAN N1220U Service Manual page 29

When the host computer sends a calibration command, the scanner performs the
calibration. Calibration is to compose black calibration data and white calibration data by
reading the black mark and white mark in the rear of the document glass as color references
for the proper color reading.
1) Black calibration data composition
Black calibration data is composed by reading and averaging 32 lines of output from the
scanning unit with the LED turned OFF.
2) White calibration data composition
White calibration data is composed by reading 16 lines of each red, green and blue of the
white mark, and averaging the highest 8 lines of output.
Above procedure is performed at high image quality color 600 dpi, color 600/300 dpi, and
grayscale 600/300 dpi and the data is stored as a file in the host computer. For grayscale
600/300 dpi, only green data is processed.
COPYRIGHT 2000 CANON INC. CANOSCAN N650U/N656U/N1220U REV.0 JUNE 2000 PRINTED IN JAPAN (IMPRIME AU JAPON)
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