[sane-devel] Canon LIDE35 color and motor issues

[Luke Campagnola]

It's been a while since I originally brought this up, but I've pulled out
the ol' scanner for another go.
to recap: color calibration isn't quite right on my canon lide35--the dark
colors drop out to black. I turned on SCAN_FLAG_DISABLE_SHADING as you
instructed, and as you predicted this recovered my lost dark colors. Where
should I go from here? Should I crank up SANE_DEBUG_GENESYS and send you the
scanimage output and *.pnm files?

Thanks, Luke


On 3/7/06, Pierre Willenbrock <pierre at pirsoft.dnsalias.org> wrote:
>
> >  - Color reproduction is better with the sane driver than the windows
> driver,
> > which tends to boost the reds way too much (yaay)
> >  - Brightness reproduction is quite poor with the sane driver. It seems
> that
> > darker colors just drop off to black very quickly.
>
> A better tool to determine if the bright and dark colors are correctly
> reproduced is a histogram tool. You can clearly see, if there is still
> room at the bottom and top of the histogram(not too much, as you still
> want some useable color values ;-)).
>
> This reveals that dark colors are cut off for the sane driver, but it
> also shows that the windows driver cuts off bright colors.
>
> Anyway, it shows a incorrect calibration on the sane side.

<snip>

> To get an unshaded image, you can disable shading correction in
> gl841_init_regs_for_scan by changing the flags(last parameter to
> gl841_init_scan_regs, currently 0) to include SCAN_FLAG_DISABLE_SHADING.
>
> If the image then still shows dark colors cut off, the offset/exposure
> calibration is to blame. Otherwise the shading calibration calculates
> incorrect data(which i suspect).
>
> I should put this lengthy description online somewhere..
>
> Regards,
>   Pierre
>
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