Re: FWA in a ColorChecker SG!?
Re: FWA in a ColorChecker SG!?
- Subject: Re: FWA in a ColorChecker SG!?
- From: Iliah Borg <email@hidden>
- Date: Thu, 27 Aug 2015 19:26:50 -0400
Dear Ben,
Either the target is from a bad batch (what's the date imprint on it?), or the measurements are bad.
On Aug 27, 2015, at 7:23 PM, Ben Goren wrote:
> I'm having a discussion with somebody over on Graeme's list for ArgyllCMS. Chad's posted a GCATS file including spectral measurements he made of a ColorChecker SG using a ColorMunki.
>
> The alternating white patches around the perimeter all show significant signs of fluorescent brighteners present. They're flat at 86% reflective from 380nm - 420nm, after which reflectively rises very steeply to a peak of about 93% at around 460nm - 470nm, and then a gradual falloff to the red but with another smaller peak at 91% at 660nm. The spectrum isn't particularly smooth.
>
> The GCATS file has a calculated XYZ value of 89.467 91.727 91.969 and a Lab value of 96.709 1.8667 -13.059, decidedly very bluish...and I couldn't even find any common RGB spaces that can encode that without clipping the blue channel.
>
> I keep thinking that Chad must somehow have gotten saddled with a counterfeit product, as I simply can't imagine something like this coming out of X-Rite. But I've also never seen a ColorChecker SG in person...which is why I'm asking here.
>
> Is the ColorChecker SG really this heavily laced with FWA? If so, why on Earth...?
>
> If not, I'll tell Chad to get in touch with somebody at X-Rite on the assumption that something's worng with his chart (or ColorMunki or _something_).
>
> b&
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Best regards,
Iliah Borg
LibRaw, LLC
www.libraw.org
www.rawdigger.com
www.fastrawviewer.com
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