Logarithmic Correction - Canon GP160DF Service Manual

CHAPTER 4 IMAGE PROCESSING SYSTEM
E.

Logarithmic correction

The CCD output has linear characteristics with regards to the reflected light from the
document, however, the density seen by the eye when looking at a document is not lin-
ear in relation to reflected light.
Figure 4-305 shows the relationship between the document density seen by the eye,
and that of the CCD output.
In order to correct this, the level is adjusted, using the correction curve shown in
Figure 4-306.
CCD output
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0
Black
Document density
Figure 4-305
4-8
White
COPYRIGHT © 1999 CANON INC.
Output level
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0
0
Input level
Figure 4-306
CANON GP160 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
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