Re: Dark scans (HP Photosmart)

Peter Kirchgessner (peter@kirchgessner.net)
Thu, 30 Dec 1999 08:35:04 +0100

Bill Wohler wrote:
>
> I've got an HP Photosmart. The scans from slides have been very,
> very dark. Almost black. I upgraded to scanimage (1.0.1) that
> has a new option called ps-exposure-time. I set this to the max
> (300%) which helped, but the scans are still way too dark.
>
> Beefing up the --brightness and --contrast options washes out the
> image.
>
> Perhaps the --custom-gamma option will help me out. How do I use it?
>

Hi Bill,

for custom gamma you need to use xscanimage. In the gamma table dialog
you can enter a gamma value of 2.0 to get some pleasing results. But you
should get similar results with GIMP. Depending on the firmware revision
of your scanner, the gamma table may be simulated in software.

> I've also tried brightening the scans with the GIMP, but I'm not
> very good and the results are not very pleasing and it takes me a
> long time to get there besides.
>
> To see whether it was the hardware or software, I tried installing
> the HP software under Windows. It scanned the slides beautifully.
> Any way to simulate the processing the HP Windows software does with
> the HP SANE backend?

Maybe Windows uses some undocumented features (btw. accessing the HP
Photosmart is not documented by HP anyway).

> What is interesting about the HP software is
> that it appears the scans are pretty dark as the scan is in progress
> (but not as dark as on the Unix side); when the scan completes, the
> dark image suddenly "brightens up".

Seems that the brightening is done in software. This should also be done
with GIMP.

>
> Any tips appreciated.
>

Sincerely

Peter

> --
> Bill Wohler <wohler@newt.com>
> Say it with MIME. Maintainer of comp.mail.mh and news.software.nn FAQs.
> If you're passed on the right, you're in the wrong lane.
>
> --
> Source code, list archive, and docs: http://www.mostang.com/sane/
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-- 
Peter Kirchgessner
WWW:    http://www.kirchgessner.net
e-mail: peter@kirchgessner.net





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