[sane-devel] Why does XSane set Gamma = 1.0

Ullrich Sigwanz us@bernafon.ch
Fri, 3 Sep 2004 16:59:59 +0200


I think I am a bit in a dilemma now.

Maybe it is because the niash scanner require a gamma <> 1.0. 
But correcting this on backend-level is not appropriate.

I think it is mainly because different frontends behave differently.

When I have a certain startup-Gamma, 

	(I am not quite sure about QuiteInSane)

keep this value and produce "perfect" scans without any additional biasing
right from the beginning.
XSane is the only frontend, that I know (which does not need to have 
any relevant meaning), that changes the gamma table before a Preview is

Is it possible to "tell" XSane somehow, which is the recommended Gamma?
Or other way round...

The original Gamma table sent to the Scanner, 
effects the analog electronics in a way that the received data 
is in the most "biased" format.

So it seems a bit artificial for me (but may be I am wrong) when 
a worse analog data format is chosen and is then extrapolated to a format,
which would already have been the best one before.

When it is possible to convert data from Gamma=1.0 to Gamma=1.6 
by software, the other way should also work, shouldn't it?

You see, the startup gamma table is "best", and there is no need to change
unless you want to achieve certain effects, which I do not dare to judge 
concerning their benefit.
When I first worked with XSane, I was always confused, why my previews were 
so dark. Having to change the gamma back to a value that lets the preview 
look reasonable, is a bit clumsy, especially when you have to do many scans.

But... Please, do not understand me wrong.

I highly appreciate your application and XSane is my favorite scanning front
Nevertheless there seems to be a small potential of improvement.

So I am not sure what to do, I have to admit.
Maybe you can help me out?

and have a nice weekend