# Re: Gamma and xsane

Oliver Rauch (oliver.rauch@Wolfsburg.DE)
Fri, 21 May 1999 14:56:38 +0200

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Chris Bitmead wrote:

> I've read a few things about what Gamma is and I think I understand it,
> but I'm still not clear on what the Gamma Slider does in xsane.
>
> Does the Gamma Slider:
>
> a) Have no effect on the resulting scan file, it merely assists viewing
> on your monitor.
>
> b) Modify the resulting scan file to look pleasant on your monitor (and
> thus render it potentially unpleasant on a different monitor).

Hi Chris,

if the gamma slider in xsane is set to 1.0 the scanned data keeps untouched,
if you select another value, the data that comes from the scanner is transformed

with the gamma value you selected. If you scan such an image into a file, the
image
in the file is transformed by the selected gamma value.

In the preview window you can see the changes you make.

>
> How does all this relate to web publishing? Let's say I found a utility
> to adjust the gamma of my monitor (apparently there is a windows utility
> at http://www.entechtaiwan.com). Let's say I adjusted it to an ideal of
> 1.0. That's wonderful for me, but then if I publish it on the web, it
> will look awful for everyone else.

If you need a gamma correction of 1.0 on your monitor, I think the contast and
brightness
of your monitor is much too high. Normally you need a gamma correction of about
1.5 - 2.5
to get good results on a monitor.
Turn down brightness and contrast.

> How does it relate to archiving images? Should I leave the gamma alone
> for an archived image and only adjust it for a web image?
>
> Also, I seem to be finding (as a newbie user of xsane who's only done a
> few scans) that the pics only look ok with the gamma turned right up.
> What does this mean?
>

Take a look at http://www.scantips.com there are good infos about scaniing/color
correction!

Bye
Oliver

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