[sane-devel] coolscan color problem

[Major A]

> -from negative film, color is really weird. This is the positive
> image, but they really don't match. I selected "Kodak negative" as
> media type.

Colour negatives need special treatment in software to eliminate the
orange mask. I don't know what xsane does in this area, but I guess it
cannot be perfect simply because the algorithm should ideally be
applied to the unprocessed data from the CCD rather than the one
processed through gamma tables etc.

> -from black and white negative, picture is really dark, and really
> grainy, and no that is not the film grain. I selected "Slide" and told
> to invert after scanning, because I don't have B&W negative type.

I think you will find satisfactory results if you play around with the
exposure and gamma options a bit.

> -from slide film, I still get grainy pictures (even though I'm
> scanning Provia or Velvia slide, both really common and one of the
> most fine grained films). I selected "Slide" as media type.

Is this really grain or just noise? In the latter case, try increasing
exposure, which will improve signal-to-noise ratio.

> In the three cases, the contrast is excessive. This is even more
> visible on slides taken by real sunny day.

What gamma settings are you using?

> Is it a known issue ? If yes, what can I do to help resolve the
> problems ? I can do whatever you want including debugging, coding and
> taking pictures :-))

Have you tried VueScan on the same pictures? If you manage to get good
scans from it, then it is a software problem.

On the other hand, coolscan2 currently allows you to set all relevant
scanner options, and with 10bit output you can get exactly the same
information as VueScan would give you. Therefore this all seems to be
a setting and/or postprocessing issue rather than a problem with the
backend.

> I'd really like to use my coolscan with SANE.

One last question: did you use coolscan or coolscan2?

> [*] I now this is the old model. That was a real bargain :-) given its
> quality.

Same here...

  Andras

===========================================================================
Major Andras
    e-mail: andras at users.sourceforge.net
    www:    http://andras.webhop.org/
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