[argyllcms] Re: help with camera profile
- From: Alberto Ferrante <alberto.ferrante@xxxxxxxxxx>
- To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
- Date: Fri, 20 Jul 2012 10:21:09 +0200
Dear Iliah,
> I agree that ufraw does not have an option for the output suitable for
> profiling.
I made some further tests and I think that the main problem is Ufraw. I
have tried building a profile by using dcraw and it seems to be better
(though, to build a profile that works in ufraw I needed to use an image
that was overexposed of 2/3 f-stops). Though, when used in ufraw, the
profile shows the same yellow cast in some situations.
>> 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.
>
> To get raw values and to confirm the uniformity you can use RawDigger,
I cannot use rawdigger as it is not available for Linux (or at least I
could not find it). I checked the raw file in ufraw with no profiles
loaded and I confirm the uniformity of illumination: there are only
slight variations on the border of the target.
What I can add is that there is the L15 patch (yellow) that is
problematic, especially with a matrix only profile (it gives errors of
about above 20-30). Though, if I make a x or l profile the peak error il
3-4.
>> 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).
>
> Sensors have very low response to UV.
I tried another profile by shooting the target in artificial light (a
430EX flash). The result is not much different, even though there is a
little bit less yellow in the images.
Any further help will be highly appreciated.
Regards,
Alberto
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