plustek: Thread: Shading problem on HP2100C and Negative scanning on EPSON

Hi there,

yesterday I found some problems in the shading correction that
affects esp. LM9831 based devices like the U12, Bearpaw 1200 and
HP2100C.
Based on version 0.44-7 I fixed that and named it 0.44-8 (to be
found in the test section at www.gjaeger.de/scanner/plustek.html).

There also seem to be some problems during negative scanning
on the EPSON Photo devices. This might be the same problem.
But I also detected here some problems in finding the correct gain values.
This is currently als a problem for my Plustek negative scans.
Till can you please try version 0.44-8 with and without calibration!
(option skipCalibration). To fix the red channel problem, you might
also use option red_gain and set this value manually to a reasonably
good value...

Thanks guys for testing
  Gerhard

I have tested the new version now. Colors of scanned negatives look 
better, at least in the preview, but when I do a real scan without 
changing any parameters before, the colors look completely different. I 
have made a screenshot of this:

http://www.linuxprinting.org/till/tmp/xsane-neg-Eps1260.png

This is done with "Negative" as scan source and "Standard Negative" as 
source type. Best colors (more or less correct, especially gray comes 
out gray) I get with "Full Range" and "Invert Colors" button (second 
from the lft in main window, directly under the adjustment sliders, or 
press Shift+N).

An there are also still these vertical stripes, which appear only for 
negative scans and were not there in 0.44-6.

Now I have done this again with "option skipCalibration 1", but this 
does not work at all. I have started with "Negative", "Full Range" and 
the color inversion button not pressed. I didn't fiddle with any 
adjustments an have taken a preview scan and then this screenshot:

http://www.linuxprinting.org/till/tmp/xsane-neg-Eps1260-skipcalibration.png

Now I have clicked (again without fiddling at any option) the "Start" 
button for the real scan. I have a resolution of 600 dpi set (This I had 
also before and there it worked). After around two seconds I get an 
error message: "Failed to start scanner: Out of memory". I click "Close" 
in the error message window and click "Start" in the main window again. 
The scan head moves 5 cm and xsane crashes with the message "Floating 
point exception (core dumped)".

The debug log of this xsane session is attached. There appeared no 
"core" file.

    Till


Gerhard Jaeger wrote:
> Hi there,
> 
> yesterday I found some problems in the shading correction that
> affects esp. LM9831 based devices like the U12, Bearpaw 1200 and
> HP2100C.
> Based on version 0.44-7 I fixed that and named it 0.44-8 (to be
> found in the test section at www.gjaeger.de/scanner/plustek.html).
> 
> There also seem to be some problems during negative scanning
> on the EPSON Photo devices. This might be the same problem.
> But I also detected here some problems in finding the correct gain values.
> This is currently als a problem for my Plustek negative scans.
> Till can you please try version 0.44-8 with and without calibration!
> (option skipCalibration). To fix the red channel problem, you might
> also use option red_gain and set this value manually to a reasonably
> good value...
> 
> Thanks guys for testing
>   Gerhard
> 
>