[sane-devel] Sane/Xsane and high resolution color negative film scans

[Oliver Rauch]

Hello Georg,

Am Sonntag, 1. Februar 2004 11:43 schrieb Dr. Georg N.Nyman:
> Hello to everyone,
> I am a semiprofessional photographer and consultant and would like to
> get a better understanding of the Sane/Xsane capabilities for my area o=
f
> interest.
> This would mean to scan color negs and color slides ( 4x5" ) with
> Sane/Xsane. Fortunatelly, one of my scanners is on the list of supporte=
d
> hardware ( Epson 3200 Photo ), two are not ( Canon 9900 F and Sony
> UY-S90 ).
> I have a few questions and maybe one of you experts can help:
> 1. Scanning negatives - in the Windows world, during the scan and its
> preview, the neg is inverted properly to judge the exposure and to make
> initial color and exposure corrections. I did sofar not find this optio=
n
> with Kooka, and with Xsane only rather imperfect.

The color correction of negatives is a bit more complex than
the color correction of photos. XSane already has a special
color correction for negatives included, but it is based on a relative
simple method.

What xsane can do is to spread the color range of the negative
to the used color range of xsane (24 or 48 bits/pixel). This is
done on a highlight+shadow compensation and a gamma correction.

With this you already can get usable results.

What you have to do is to tell xsane how to spread the color range.
To do this eactivate in the preferences menu the option
"edit medium definition". When you did this then there is a little slider=
-icon
displayed next to the medium definition menu and  the Buttons
"R" and "M" in the xsane main window are replaced by
a negative icon (store definition) and a crossed negative icon
(delete definition).

You should enable the collor correction for each color now, then
you have a common slider (gray) and one for red, green and blue.

Now you should scan some slides that are taken with the same negative fil=
m,
especally with bright and dark parts in it. You have to try a setting tha=
t
does not cut any dark or bright colors (highlight and shadow or contrast =
and=20
brightness) in any images and gives relative natural colors (gamma).

When you think you found a good setting then save it under the name
of the negative film.

Then disable the option "edit menu definitions" and select the
juest created medium definition. Do a preview scan.
You now should be able to get relative good results with
a color correction.


> 2. Once a preview scan of the whole scanable area was made, it would be
> fine to make a more detailed preview scan of the selected image area to
> properly determine the area to be scanned...

For XSane:
Select an area in the preview window and press the zoom into selected are=
a
button in the top of the preview window. When you do a new preview scan
now then this is done with a higher resolution.

You also can define an oversampling factor for the preview in the
Preferences-Setup->Display part. When you enter e.g. a value of
2.0 then the preview is done with double resolution.
Example: Preview window size is 100x150 pixel. The scanned
preview has a size of 200x300 pixel.

> 3. Scanning large format transparent items means that the size
> adjustments of the scan need to show lower % values than currently
> available - 35% is not small enough. I would need to reduce it to value=
s
> down to 10% and even sometimes a bit less.

Do you talk about the xsane viewer?

Oliver

--=20
http://www.xsane.org
http://www.rauch-domain.de
http://www.sane-project.org