Re: Calibration problem on UMAX Astra 1220S

Oliver Rauch (oliver.rauch@Wolfsburg.DE)
Fri, 26 Mar 1999 21:25:32 +0100

Dean Martin Townsley wrote:

> > It has nothing to do with you problem!
> >
> > What you are looking for is higlight and shadow (or black and white point)
> > definition.
> > The Astra 1220S only can do this via gamma correction, there are no seperate
> > functions
> > for this.
>
> Is it possible to make the popup help more informative on this point? Like maybe:
> "Do a quality (rather than quick) internal white-calibration"
> The point is to distiguish it from calibration on the image. You can decide if
> this is necessary since the real problem here is that my scanner just
> doesn't have a very good white point whether it's calibrated carefully or not.
> Sounds like this option adresses the problem of vertical streaks more than my
> problem, so maybe it should say something more along those lines, I don't know.

I don`t see a problem with the current tooltip because it exactly describes what it
is,there is nothing written about calibration on image - but I will think about a change
of the text.

> > Xsane makes available the highlight and shadow function via the hystogram window.
> > Open the histogram window, between the two histograms there are some colored blocks.
> > In the recent version there are three sliders in the gray block. Move the mid slider
> > and
> > the left slider to the right, as far as possible. Then do a real scan of the image.
> > On a preview
> > you will not see any differences, because the preview is always done in 24bpp, the
> > real
> > scan uses a 36bpp and afterwards converts it to a 24bpp image.
> >
> > I hope this works for you!
>
> Actually this helps a lot! Thanks for the pointer. The scan comes out actually
> useful though it's still not as good as the one done on another scanner. I'm kinda
> new to scanning so I don't know many tricks yet.
>

Fine!

> In the end I have decided the white point on this scanner is just not so good for
> whetever reason. I can put in something white and something slightly off-white
> and even using only the top half of the values as described above they both come
> out completely white, indicating the scanner can't see the difference between
> them. Oh well that's why it's not an expensive scanner I suppose (I use it mostly
> for 1-bit scans of text anyhow), though I really have no way of knowing if it's
> the model or just this one scanner.
>
> Thanks for all of your help Oliver, and thanks for your work on the software!
> -Dean Townsley
>

The umax Astra scanners a very good for their price. You can get a scanner that
supportsanalog gamma, highlight and shadow function - that's what you want - but for
these scanners
you have to pay 5 - 10 times the price you paied for your scanner!

Bye
Oliver

--
EMAIL: Oliver.Rauch@Wolfsburg.DE
WWW: http://www.wolfsburg.de/~rauch

--
Source code, list archive, and docs: http://www.mostang.com/sane/
To unsubscribe: echo unsubscribe sane-devel | mail majordomo@mostang.com