Ricoh Aficio 220 Service Manual page 59

IMAGE PROCESSING 20 September 1999
Smoothing Filter Adjustment - Photo Mode
When the user selects "Service Mode" for Photo original type, the smoothing filter
can be changed with SP4-927. A stronger smoothing filter makes the image more
blurred (1: Weak ~ 8: Strong).
Smoothing Filter Adjustment - Text and Text/Photo Modes
To reduce the possibility of moiré, a small-matrix smoothing filter is used after
scanner gamma (γ) correction in the Text and Text/Photo mode.
This is only used when the user selects "Service Mode" for either Text or
Text/Photo original type. The level of smoothing can be adjusted with SP4-921.
Independent Dot Erase
In Text mode and in Text/Photo mode, independent dots are detected using a 7 x 9
matrix and erased from the image.
The independent dot detection level can be adjusted with SP4-917 (for the original
modes known as "Service Mode") and SP4-944 (other original modes – on/off only;
no adjustment). With a larger SP setting, more dots are detected as independent
dots and erased, even if the dot's density is high. However, dots in mesh-like
images may be detected as independent dots mistakenly.
Independent Dot Erase after Binary Picture Processing
Normally, independent dot erase is done in the filtering stage. However, when the
user selects "Service Mode" for Text original type, independent dots may reappear
in the image after the binary picture processing. These independent dots are
erased after gradation processing.
SP4-939 changes the filter that is used for this process, and it can be also used to
disable this feature. A smaller matrix is more likely to remove dots.
2-24