Logarithmic Correction And Bgr-To-Ymc Conversion; Logarithmic Correction; Bgr-To-Ymc Conversion4-11 - Canon CLC 1120 Service Manual

I.

Logarithmic Correction and BGR-to-YMC Conversion

a. Logarithmic Correction
The output of the CCD possesses linear characteristics in relation to the intensity of light
reflected by an original. The density as perceived by the eye, however, does not necessarily have
linear characteristics.
To compensate for the discrepancy, the copier performs level conversion as shown in Figure 4-
408.
b. BGR-to-YMC Conversion
The intensity of light passing through each of the filters (B, G, R) of the CCD and the density
of (Y, M, C) of an original are in a complementary relationship, enabling level conversion (B to Y,
G to M, R to C) as shown in Figure 4-409 and generation of Y, M, and C signals.
Output level
255
0
Input level
Figure 4-408 Logarithmic Correction
COPYRIGHT © 1999 CANON INC.
255
CANON CLC1120/1130/1150 REV.0 MAR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE PROCESSING SYSTEM
Output level
(Y, M, C)
255
Darker
Lighter
0
Input level (B, G, R)
Figure 4-409 BGR-to-YMC Conversion
255
4-11