>
> From: Oliver Rauch <oliver.rauch@Wolfsburg.DE>
> Dean Martin Townsley wrote:
>
> > Hi all,
> > My problem with the calibration is simple: I can't get it to perform the
> > calibration. I'm using sane 1.00 with the build-1 patch for the umax drivers
> > and xsane 0.18 for the frontend (tried xscanimage too).
> > I stuck a debug message in the code to supplement the messages already
> > there and found that dev->do_calibration was zero when the scan process went
> > through the do_calibration() function even when the box for "Quality
> > Calibration" was checked in the interface. The code checks and to me seems
> > to only perform the calibration if this is nonzero. I don't know if this is
> > a problem in the driver itself or somewhere else but both xsane and
> > xscanimage exhibit the same problem. That's as far as I got, I have final
> > exams for the next two days (take homes) so I won't be able to fiddle again
> > until after that probably, but I figured I'd say something so someone with
> > better knowledge of the code can maybe investigate.
> >
> > oh, btw, /proc/scsi/scsi says
> > Host: scsi0 Channel: 00 Id: 05 Lun: 00
> > Vendor: UMAX Model: Astra 1220S Rev: V1.1
> > Type: Scanner ANSI SCSI revision: 02
> >
> > Which I presume means it's firmware 1.1, (out of a possible 1.5, ugh).
> >
>
> Hi Dean,
>
> like described in the sane-umax-docs the quality calibration does not work with
> all scanners!
I thought I remembered seeing this but still can't find it on the web page at
least. So which ones does it work with?
> What happens or does not happen if you enable quality calibration?
Okay I'll let you know the story. I'm trying to scan a card that's basically
an embossed white graphic on a slightly off-white background. Well, the
scanner sees that the thing is almost totally white, and saturates the scan
really bad. The histogram in xsane does not fall off at the high
Luminosities, it just saturates. From looking at other stuff on the net,
this appears abnormal, even for stuff on white backgrounds. I am under the
ipression that this is what the "Quality Calibration" is for (though I could
be wrong) is to set the white point so that it is not out of the scanner's
sensing range, as it apparently is on mine since white and off-white come up
as the same color -- ffffff white. I would assume it's just an impossible
scan but someone else did it on another scanner and it came out fine, I'm
just trying to match that (and not even coming close).
Now for what happens when when I try to use the calibration. Nothing.
There is no noticable difference in the scans or the activity performed by
the scanner. I assume that even if the firmware is doing the calibration
that it still has to DO something i.e. the lamp has to move prior to the
actual scan. (Again I could be wrong let me know if I am) In my case I find
no difference between having the button checked or not in the frontend.
> Background:
> There are some problems with calibration by driver. UMAX uses a different
> kind of calibration for each scanner model and firmware. I only know the one of
> the Umax Supervista S12 with firmware 2.0.
>
> If you set the quality calibration button, the driver requests a quality
> calibration
> from the scanner. If the scanner is not able to do the quality calibration on
> its own,
> it requests the driver to do this. In that case do_calibration is set in the
> driver.
> Then the scanner sends the calibration data, the driver does the calibration and
>
> sends back the calibration data.
>
> If the scanner does not request that the driver has to do the calibration, there
> is
> nothing what the driver can do.
Hopefully I'm not totally off base here. I think my scanner is capable of
doing calibration, since the starting of the driver says
[umax] f/w support function:
[umax] ---------------------
[umax] quality calibration
but it likely performs it in the firmware, since the
"change" to firmware 1.5 for this scanner was to add software calibration.
I think I could do better if I had an idea what I was looking for. What is
the Quality Calibration supposed to work like? Should it happen at the
beginning of each scan when the button is checked? Should the scan process
be different? A two pass scan maybe? If it's not working is this because
the driver is just not telling the scanner to do it properly? Is this
documented anywhere or is this a trial and error type thing?
>
> Bye
> Oliver
>
Thanks for the help, and thanks for your work on the driver, it scans
photographs great!
Regards,
-Dean Townsley
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