Service manual

COPYRIGHT © 1999 CANON INC. CANON GP160 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE PROCESSING SYSTEM
4-8
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.
Figure 4-305 Figure 4-306
25
0
Black White
CCD output
Document density
25
0
025
Output level
Input level
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