[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. 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.


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