[argyllcms]
- From: "alberto.ferrante@xxxxxxxxxx" <alberto.ferrante@xxxxxxxxxx>
- To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
- Date: Thu, 19 Jul 2012 14:30:45 +0200 (CEST)
Dear Stephen,
> 1. Ufraw is based on dcraw but it does some weird
scaling of the linear TIFF
>data.
>Output the same raw photo of the
camera target as a linear TIFF in ufraw,
>dcraw, DarkTable and in Raw
Therapee.
>Compare the scanin results: ufraw is anomalous.
>Ufraw also
lacks tools like RGB tone curves that are most useful for rendering
>the output.
I am aware of that, but I need a profile for ufraw.
Eventually, in the long term, I may abandon ufraw as it is not
developed anymore and it has some things that I don't like (mostly it
is just maintained), but for the moment I have all my flow designed
around it and I am not willing to change.
> 2. It is really difficult
to control glare (flare) and get good uniformity of
> REFLECTANCE when
shooting in sunlight. An incident light meter is not helpful.
> Check
the average RGB around the edges of the target in ufraw. If the
variation
> is more than 2 or 3% then the profiling will likely have
problems.
I will check that again, I haven't done it in a
"scientific" way, but just taking some reads on the border of the
target (in ufraw) it looked like quite uniform.
> Secondly, noon
sunlight is not D50.
Yes, I know that, but I am not aware of any other
reasonably cheap light source for this purpose, considering that I am
doing these profiles for personal use.
To be honest I also tried with
an artificial light (that is not D50 anyway) and the results have not
been much different.
> 3. The IT8.7/2 target has a good spread off
patches but the Kodak paper has
> flourescent whitening additives. The
target white point will not be neutral in
> direct sunlight (lots of
UV).
That is something I noticed, yes.
> 4. Digital cameras have good
system linearity and a simple matrix profile
> should be satisfactory.
The ColorChecker Classic 24 has good spectral
> properties (more
natural than IT8.7/2), is adequate for matrix profiles,
> reasonably
priced and well-supported by Argyll CMS and other profiling software.
I will check that.
> What you get in the end is a rough and ready ICC
matrix profile that should
> deliver realistic colour for sunlight and
similar daylight illuminants.
So far I have used the profiles for my
other cameras with satisfactory results. Of course I know that these
profiles are not perfect, but they work quite well, I assure you.
Regards,
Alberto
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