Re: Lab and visible colours
Re: Lab and visible colours
- Subject: Re: Lab and visible colours
- From: Giordano Galli <email@hidden>
- Date: Thu, 6 Jul 2006 16:18:49 +0200
Hi Graeme
Thank you very much for your reply.
One of the troubles is that it's hard to define the 'human gamut'.
For strictly reflective sources, it is reasonably easy, because
the reflected light energy is limited by that of the illuminant,
and the illuminant is generally chosen to be a reasonable
one (ie. Daylight, uniform spectrum, etc.).
For emissive sources, there are no such constraints,
the light energy can be any wavelength, and any intensity.
It's therefore theoretically possible to infinitely extend
the 'human gamut' in the purple direction, simply by
increasing the lighting intensity (at least until your
eyeballs burn out !)
My mistake. x:)
I was indeed aware of this inherent variability of our gamut.
I should have made it clear that I'm after a set of (would I
dare to say 'morphological'?) characteristics rather than a
precise gamut shape and volume.
As an example, I'd like to understand whether the absence of
dark colours in the b>0 region is a constant (this, somehow,
relates to a discussion we had a while ago about the 'native'
brightness of hues) as it would significantly reduce the number
of colours that rgb devices can't analyse/reproduce.
As a side note, while thinking over your reply I realized that
plots of Lab images in ColorThink Pro clip colours to a portion
of the Lab parallelepiped; interestingly enough, the biggest
cut could be roughly identified as the b>0 L<b*0.7*(100/127)
region. Unfortunately, I couldn't verify whether this feature
has anything to do with our discussion, as Chromix seems to have
recently determined to programmatically ignore my posts on their
forums.
[I haven't got around to trying this trick in practice yet,
to see how usable it is. It would help to have a nice bright LCD
display to try it on..]
Having spent the last 20 years working with CRTs, maybe I'm
not entitled to qualify an LCD as anything less than "nice
bright"; that said, I have a brand new Eizo CG220 I'd be more
than happy to test your trick with, should this be of any
interest to you (if you prefer so, you can reach me at
email@hidden).
Btw, a white level measurement for this device carried out
in BabelColor using an Eye-One Pro in emission mode yields
220 cd/m2.
Thanks a lot!
Giordano
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