Re: WB, Gray Cards and Cloudy Days (Graeme Gill)
Re: WB, Gray Cards and Cloudy Days (Graeme Gill)
- Subject: Re: WB, Gray Cards and Cloudy Days (Graeme Gill)
- From: Louis Dina <email@hidden>
- Date: Mon, 19 Aug 2013 16:40:00 -0500
Thanks, Graeme.
Wow...there is a lot of information that comes up from a search for "Color
Appearance Models" by Mark Fairchild! I'm looking for the "lite version"
for the lay person and will look around to see what I can find. Even if I
don't understand it all, especially the math, hopefully I will gain a
better understanding of how it all works (according to the model, anyway).
Regards,
Lou
> ------------------------------
>
> Message: 4
> Date: Tue, 20 Aug 2013 00:38:16 +1000
> From: Graeme Gill <email@hidden>
> To: ColorSync <email@hidden>
> Subject: Re: WB, Gray Cards and Cloudy Days
> Message-ID: <email@hidden>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Louis Dina wrote:
> > I'd like feedback on this topic, especially if there are any hard color
> > science and studies to back it up. I'm also interested in general
> opinions
> > and observations, even if not backed up by science.
>
> Hi,
> there is an awful lot of literature about chromatic adaptation
> out there, if you go looking for it. One summary close to hand
> for me was "Color Appearance Models" by Mark Fairchild.
>
> > If I use a spectrally neutral gray card on a heavily overcast day, and
> use
> > it to set WB in my Raw Converter, I usually find that my images end up
> > being much warmer than the scene I perceived.
>
> This may not be too hard to explain. Chromatic adaptation to a display
> screen
> is typically close to complete, since often there are many white or grey
> samples in your field of view. In general though, chromatic adaptation
> may not be complete, and is the product of many visual and cognitive
> mechanisms. If the prevailing color of a heavily overcast day is towards
> blue, and especially if it is off the blackbody or daylight illuminant
> locus
> (I'm not sure if that can be the case - it would be interesting to
> measure it), then perhaps you don't fully chromatically adapt to that
> color,
> so the overall appearance is cold - ie. your visual white point reference
> is in a slightly warm direction from the scene illuminant. If you normalise
> (ie. "chromatically adapt") your photo fully to the illuminant color,
> then naturally it will look warmer than your partially chromatically
> adapted visual impression of the real scene.
>
> Graeme Gill.
>
>
>
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