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Shading Correction
Shading Correction compensates for non-uniform illumination, lens vignetting as well as any differences in pixel
sensitivity. The signal from a white homogeneous background is obtained and used as a reference to correct each
pixel of the sensor with an individual factor, scaled up to the intensity maximum (255 at 8-bit resolution and 4095 at
12-bit) to provide a flat signal. The reference signal is stored in the Shading Correction Memory (SCM) of the camera
and subsequent scans are normalized using the scale factors from this white reference.
•
Open the "Shading Correction" dialog (Alt+s).
•
Use a homogeneous white object to acquire the
reference data, e.g. a white sheet of paper.
•
Either take a 2-dimesional scan ("Area Scan
Function" [F3] ) or
use a single line signal that was averaged over a
number of single line scans.
•
To suppress any influence of the surface structure,
move the imaged object during the image acqui-
sition.
•
Input the scale range:
Minimum in %: intensity values lower than
"Minimum" will not be changed.
A typical appropriate value is 10% of the full
intensity range, i.e. 26 (= 10% · 255) for an 8-bit
intensity scale.
Maximum in %: target value for scaling
A typical appropriate value is 90% of the full
intensity range. The result will be a homogeneous
line at 230 (= 90% · 255) for an 8-bit intensity scale.
After shading correction, the line scan signal has a homogeneous intensity at 255
16
Shading Correction dialog
(8 bit, Maximum 100%)
SK7500GTO-XL Instruction Manual (11.2015)
3 Camera Control and Performing a Scan
Click on button New Reference
•
•
Click on Save SCM to Flash to save the SCM
reference signal in the flash memory of the camera
Once the reference signal is copied from the shading
correction memory (SCM) to the camera flash
memory it will persist even after a power down.
On a re-start, this data will be restored from the flash
memory back to the SCM.
The current shading correction status - active or not
active - is also retained on power down.
ON
Activate Shading Correction with the reference
signal which is stored in the SCM.
OFF
Switch off Shading Correction. The Shading
Correction is not retained in camera flash
memory at the next start – even if the SCM data
has already been saved into the flash memory
previously.
Load File to SCM
A stored reference signal will
be loaded in the SCM of the camera. If the load
process completes then the Shading Correction
is active.
© 2015
Schäfter + Kirchhoff GmbH • Hamburg
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