[argyllcms] Re: help with camera profile
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 29 Jul 2012 14:45:42 -0700
On 2012-07-29, at 12:55 PM, Iliah Borg wrote:
>> If I try to do the same with the 7D profile, the error gets higher (27
>> as peak) and even after removing 3 patches it stays to 17. The "bad"
>> patches are always orange/yellow.
>>
> it might depend on the output colour space and how they get their. I mean,
> have you checked for clipping?
Iliah's excellent point deserves a bit of expansion. For example, sRGB is only
big enough to encode 96% of the ColorChecker gamut, and only 83% of the Digital
ColorChecker gamut. Indeed, there isn't a single standard reference chart that
sRGB can entirely encode without clipping:
http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html
If you follow the link on that page to his ColorChecker calculator, you'll see
that the cyan patch needs a negative red value in sRGB. I don't think it's
quite enough to account for a double-digit DE error, but I can't do that kind
of math in my head...besides which, the classic ColorChecker orange / yellow
patches are well within the sRGB gamut.
If you don't want any clipping in any of the standard charts, there're only two
working spaces to pick from: the oversized ProPhoto RGB, and Bruce's own Beta
RGB. If you're using Adobe products, your only choice for color space after raw
conversion to avoid clipping is ProPhoto, since it doesn't support Beta RGB.
Canon's Digital Picture Professional doesn't even give you that choice. As they
say, your mileage not only may vary, but it's pretty much guaranteed to....
Cheers,
b&
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