[sane-devel] Reflecta DigiDia 5000 not found

[Reinhard Kotucha]

On 2017-12-27 at 11:28:58 +0100, Klaus Kaempf wrote:

 > * Reinhard Kotucha <reinhard.kotucha at web.de> [Dec 23. 2017 23:52]:
 > > 
 > > The next problem to solve is to find a suitable ICM file for this
 > > scanner.  Colors are still too dark and incorrect
 > 
 > Happened to all of my slides too. I used gimp to normalize colors and
 > had spectacular results.

Hi Klaus, Julian, and Dave and thank you very much for your
suggestions.

As I mentioned in a previous mail, there was a file on the CD called
"Generic Positive.ft".  The file format is neither understood by sane
nor by me.  The good thing is that it's pure ASCII.

I first extracted the lookup table

FilmLut		
	0.00 	0.00 	0.00 
	7.50 	7.50 	6.00 
[...lines omitted...]
	4094.11 	4094.09 	4094.43 
	4095.00 	4095.00 	4095.00;

and plotted the curves.  See

   http://ms25.ddns.net/plot-lut.pdf

The first page contains a linear plot, the second page shows the same
plot scaled logarithmically.  Please note that when scaled
logarithmically, the Gamma value is just the slope (dy/dx) of the
curve.  As you can see, two different Gamma values are used.

I then loaded a scanned image into Gimp and adapted the curves
according to the linear plot.  The results were amazing.  I did not
expect to get such good results almost immediately.  But the result
isn't perfect.  It turned out that the lower left part of the curve is
extremely critical.  Small changes make huge differences and there is
no way to get things correct if the only tool you can use is a mouse.

The next step is to write a script which applies the lookup table to
pnm files.  The pnm file format is quite simple and I think that I can
write such a script within a reasonable amount of time.

I could probably improve the results if anybody tells me what these
values mean and how to apply them:

  FilmMatR    1.4234   -0.3230    0.0061   -29.7088; 
  FilmMatG    0.0600    0.9677    0.0719   -31.3147;
  FilmMatB    0.1562   -0.5104    1.4530   -28.9059;

I suppose that I can scan all my slides automatically now and can
apply the color profile of my scanner afterwards.  Everything I can do
without manual interaction is fine for me (I've abt. 7200 slides) and
GUI tools are not very helpful at this stage.  I'm sure that GUI tools
like GIMP are helpful in order to enhance individual images.

Regards,
  Reinhard

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Reinhard Kotucha                            Phone: +49-511-3373112
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