Minolta CF910 Service Manual page 44

8 AE Processing: PWB-C
<Histogram Making>
• The scanning area is divided into two in the feeding direction [at a point 216 mm
from the trailing edge of the original (excluding the edge)].
The area is not divided if, depending on the size of the original, the division point
falls within, or outside, the edge on the leading edge side of the original.
• Lightness data readings are tallied up for each four gradation levels using the
image data sampled through "Histogram Making."
• The lightness data readings tallied up for each four gradation levels and in two
parts are totaled to generate one lightness histogram (for AE processing).
<AE Level Evaluation>
• From the histogram with lightness blocked into four gradation levels, the local
maximum value of each block (gradation level with the greatest frequency in each
block) is extracted.
• Calculation is made to determine if there is any gradation level extracted, the sum
of frequency of ±8 gradation levels of which accounts for 12.5% or more of the
sum of frequency of the entire original. (Processing is done in the order of the gra-
dation level of higher lightness.)
• If there is, AE level (local minimum value) is set at the lightness level which is 1/16
or less of the lightness frequency at that local maximum value.
• If not, the AE level is determined according to the original mode.
• The AE processing table is determined based on the AE level.
• Background processing (AE processing) is performed as the AE processing table
is determined.
Divided into two in FD direction
Leading edge
of original
Lightness histogram
Frequency
Monochrome
Color
Low
If a foggy background is produced despite the AE processing, further adjustments
can be made with "AE Adjust" of "Image Adjust" available from the Service Mode
menu.
Division point
Edge
Edge
Original
Edge
216mm
Feeding Direction
4 gradation levels
Lightness
M-27
Edge
Trailing edge
of original
Local maximum value
[AE level setting according to original mode]
Original mode
Map
Photo
Text
Text/photo
1154M080AB
High
Crosswise
Direction
1154M079AA
AE level
224
240
104 - 240
136 - 240