Background Erase - Gestetner A294 Service Manual

Rev. 2/2000

2.3.6 BACKGROUND ERASE

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Background Erase
The background erase process is used only when setting of SP 4-903-70 to 74 is
changed from the default setting (the default is 'disabled').
Usually, dirty background is erased using Auto Image Density (ADS). Background
Erase should be used when ADS cannot fully erase the dirty background.
There are two Background Erase modes. The one that is being used depends on
the SP mode setting. Setting 2 has a stronger effect than setting 1, but setting 2
may cause sudden changes in the data around the threshold level.
Setting 1: MTF correction is not applied to any low image density data that
remains after auto shading if the data is lower than a threshold level [A].
The overall effect is to reduce the background in a similar way to that
shown by the dotted line in the diagram. This process can be applied for
each image mode (except for photo mode) by changing the setting of
SP4-903-70, 72, 73 or 74.
Setting 2: Any low image density data that remains after auto shading will be
treated as "0" if the data is lower than a threshold level [A]. The
background is cut off as shown by the solid vertical line in the diagram
at [A]. This process can be applied for each image mode by changing
the setting of SP4-903-70, 71, 72, 73 or 74.
The thresholds can be changed with SP4-903-65 to 69.
SM
CÓPIA NÃO CONTROLADA
0
[A] (Threshold)
2-27
CÓPIA NÃO CONTROLADA
IMAGE PROCESSING
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A294D591.WMF
A294/A295