Shading Adjustment; Shading Correction - Canon imageRUNNER 2525 Series Service Manual

There are two types of shading correction: shading adjustment performed in the Service mode and shading correction performed
for each job.
● Shading Adjustment
The machine measures the density of the standard white plate, and stores the measured density data. It then processes the
stored data to use it as the target value for shading correction.
● Shading Correction
The machine performs shading correction for each scan. It measures the density of the standard white plate, and compares the
measured value with the target value stored in the shading correction circuit to use the difference between the two as the shading
correction value. The machine uses this shading correction value to correct the variation among CMOS sensor pixels when
scanning the original, thus evening out the image density level.
CMOS
sensor
output
Target
value
Measurement
value
Characteristics
after correction
Characteristics
before correction
White
Original density
Standard white plate
35
2. Technical Explanation