I've compiled the updated PR1996 and ran some tests. First using the
Rec2020 as output profile, but distinct posterization was visible in
comparison to e.g. sRGB.
Then, I installed eciRGBv2 in Darktable, which is one of the profiles
suited well to scans with the intention to print them and my default
"scan-to" profile. I exported a non-compressed TIF in Darktable with
eciRGBv2 using its internal CMS, which probably uses a perceptive
rendering (?), and opened this exported TIF in Photoshop. At the same
time I opened the original LAB scan in Photoshop and performed a
conversation into the eciRGBv2 profile using perceptive rendering
without blackpoint compensation. Both images now look like twins,
totally identical, with identical histrograms! Photoshop's histogram
statistics report the same average and deviation down to the last digit.
I think we can say: mission accomplished! Astonishing speed of
implementation.
Will the feature be publicly available with a v2.6.1 release or is it
restricted to v2.7 developement?
Thanks a lot for all the work,
Christian
Am 15.01.19 um 18:37 schrieb Ulrich Pegelow:
Am 15.01.19 um 15:33 schrieb Christian Stromberg:
Hi,
thanks for the hints! It took me some time to fill up all missing
dependencies. Because it's the first time I am compiling a whole
program, I wasn't familiar with the specific library names for Linux
Mint. Looking them up and installing them while continuously running
the built script to see if a missing component was successfully
installed took the largest part of the time.
I've got the new version running and from my point of view, I can
happily report that the display of the files is absolutely identical
(see attachments). Thank you very much for your efforts!
Nice to hear!
Is sRGB know just used for displaying or is the export output also
restricted to sRGB?
Export is not restricted, you may chose the output gamut from some
pre-defined profiles and you may also use third party profiles.
However, right now PR1996 would be limited to sRGB on the *input* side
when it comes to CIELAB or ICCLAB Tiff files. Color dynamics outside
of sRGB is lost for these files.
The color profiles of the scanners I sent you have been created using
IT8 targets. So the range of colors included in these profiles is not
theoretical but a practical measurement using real slide films
showing IT8 color tables and correcting the scanners colors by using
lab measurements that are provided alongside the IT8 slide film
targets. This is also the reason why, using the same Fuji Provia 100F
IT8 target, the range of colors within the ICC profile of the Tango
is much larger than that of the Nexscan: the Tango is a drum scanner
while the Nexscan is a CCD based flatbed scanner.
I've checked your profiles and they are significantly larger than sRGB
or even AdobeRGB. In order to cope with these colors we would need to
internally convert to a wide gamut profile. Rec2020 and ProPhoto come
into mind. As darktable has already Rec2020 defined, this would be my
profile of choice in this case.
I'v just enhanced PR1996 accordingly.
Ulrich
But if export is not restricted to sRGB and it is just the displaying
part that uses sRGB, I would think that most users can live with that
just fine.
Best wishes,
Christian
____________________________________________________________________________
darktable user mailing list
to unsubscribe send a mail to
[email protected]
____________________________________________________________________________
darktable user mailing list
to unsubscribe send a mail to [email protected]
