[sane-devel] Canon LIDE35 color and motor issues

[Pierre Willenbrock]

Hi Luke,

I did rewrite some parts of the calibration, so there may be some
improvements/regressions. Please test the attached patch, it applies
against current cvs. I only need the stderr output this time. Try 75 dpi
and 1200 dpi, they use different ccd-modes.

As you very probably already realized, the sane-devel list has a mail
size limit of 50kb(*6/8 for binary data). If the (compressed)log is
larger than that, please reply only to me.

Regards,
  Pierre


Luke Campagnola schrieb:
> I actually hadn't tried CVS, which was silly, but it turns out the problem
> is a little worse there.. the darks may be slightly better but now the
> lights are clipped too. I've attached output + pnms.
> 
> Thanks.
> 
> On 1/4/07, Pierre Willenbrock <pierre at pirsoft.dnsalias.org> wrote:
>>
>> Luke Campagnola schrieb:
>> > 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
>> >
>>
>> Hi Luke,
>>
>> Did you try with sane from cvs? There have been some bug fixes. If that
>> does not show the dark colors, use SANE_DEBUG_GENESYS=255 and
>> SANE_DEBUG_GENESYS_GL841=255 with scanimage in color mode, and send the
>> resulting error output and the generated .pnms.
>>
>> Regards,
>>   Pierre
>>
>> >
>> > 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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