Henrik Andersson schrieb am 07.12.2014 um 14:30:
Regarding LZW compression, that is a non destructive compressions
(lossless) and shouldn't
affect your result the way it did in your compare. Something definitly
got wrong on the way.
sorry for answering late, but I didn't have the time to go on on that
project for the last week or so.
Thanks to Steven - you pointed me to the right direction, and Henrik is
also right.
I used XnViewMP to convert from 48bit to - what I thought - 48bit LZW,
since it didn't show up any dialog about color depth. I was wondering
that the pictures were only 1/3 of the original size - it also reduced
color depth to 24bit per pixel while converting. So this is the
explanation for the artefacts.
This afternoon I had been fiddling around with a base curve for my color
negatives:
In the past I shot an IT8 Target by Wolf Faust on my favourite color
negative films and can use this as a reference since darktable gives Lab
with the color picker and Wolf gives Lab in his reference file for the
gray steps at the lower end of the target also. But it takes some time
to work out. As of now it looks something like the attached file for a
Kodak Portra 160VC.
I'm going to scan a test film of real pictures and will see how it works
out.
My only concern is file size - around 180MB per file out of Vuescan in
RAW mode with IR channel included - thus 64bit/Pixel.
@Henrik: My workflow is similar to yours:
1. Invert 2. crop and rotate 3. white balance 4. base curve 5. exposure.
This is done to every image (1-4 in batch mode), the rest is individual
correction based on the picture content.
--
regards
Bernhard
http://www.bilddateien.de
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