E2v UNIIQA User Manual - page 38
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7.9.1 Automatic Calibration
Low Filter FFC With (
LowFilterFFCWidth
) : Set and Enable/disable the Flat Field Correction Low
Band Filter. This command is available in the CommCam “Flat Field Correction” section :
Read function (ASCII): “r lffw” : Returns the FFC Status : 0 to 127 (0 if disabled, X>0 enabled
and set at X)
Write function (ASCII):
“w lffw
is 0, then the Low Band filter is disabled
When you can’t provide a moving Target to the Camera during the PRNU Calibration you can
setup the FFC Low Band Filter in order to remove the defect from the Target before calculating
the FFC parameters. The Value set in the FFC filter defined the size of the interval around each
pixel : The Filter will replace each pixel value by the average on the interval.
The FFC Low band filter is just an help to make in use the FFC (PRNU part) more easily :
This can be done with a non-moving white paper as its defaults will be filtered in order to
not being taken in account in the PRNU Correction.
Don’t forget to reset the filter (to “0”) after usage.
FFC Low Band Filter.
The FFC Low Band Filter allows an easier make in use of the FFC (PRNU Part) : You can use
a non-moving paper and you can filter the defects of these paper before the FFC
calculation in order to not take them in account.
The command “lffw” set the intervals (+/-) around each pixel for the average calculation.
Each pixel is then compared to the average on the interval around it and replaced by this
average if the difference is too high. With a filter value set at “X”, the calculation interval
will be [-X , +X] around the pixel position.
A large interval value allows filtering big defects on the paper but finally the setting of this
interval depends also on the magnification in the system.