CIE Lab Color Coordinates?

OR
Posted By
Owen Ransen
Oct 13, 2006
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1388
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5
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Someone here must know this….

What are the full extents of the CIELab ab axes?
L is from 0 to 100 I think.
a is from ? to ?
b is from ? to ?

Adobe gives byte values but I am talking about
the international standard CIE values….

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MH
Mike Hyndman
Oct 13, 2006
"Owen Ransen" wrote in message
Someone here must know this….

What are the full extents of the CIELab ab axes?
L is from 0 to 100 I think.
a is from ? to ?
b is from ? to ?

Adobe gives byte values but I am talking about
the international standard CIE values….

Owen,

Very heavy ;(

I know the axes are not linear (cubic root law?) , have a wade through http://www.fho-emden.de/~hoffmann/cielab03022003.pdf

MH
OR
Owen Ransen
Oct 14, 2006
On Fri, 13 Oct 2006 20:58:08 +0100, "Mike Hyndman" wrote:

"Owen Ransen" wrote in message
Someone here must know this….

What are the full extents of the CIELab ab axes?
L is from 0 to 100 I think.
a is from ? to ?
b is from ? to ?

Adobe gives byte values but I am talking about
the international standard CIE values….

Owen,

Very heavy ;(

I know the axes are not linear (cubic root law?) , have a wade through http://www.fho-emden.de/~hoffmann/cielab03022003.pdf

Thanks, I’ll have a look.

I don’t need to know exact values, just need to have an order of magnitude. So I think I’ll take a ton of samples using a spectrometer to get an idea of the real-life range.

Easy to use graphics effects:
http://www.ransen.com/
OR
Owen Ransen
Oct 14, 2006
On Fri, 13 Oct 2006 20:58:08 +0100, "Mike Hyndman" wrote:

I know the axes are not linear (cubic root law?) , have a wade through http://www.fho-emden.de/~hoffmann/cielab03022003.pdf

It looks like the gamut for the human eye is roughly
-200 to + 200 for both a* and b* .

Thanks for pointing me to that source!

Easy to use graphics effects:
http://www.ransen.com/
MH
Mike Hyndman
Oct 14, 2006
"Owen Ransen" wrote in message
On Fri, 13 Oct 2006 20:58:08 +0100, "Mike Hyndman" wrote:

I know the axes are not linear (cubic root law?) , have a wade through http://www.fho-emden.de/~hoffmann/cielab03022003.pdf

It looks like the gamut for the human eye is roughly
-200 to + 200 for both a* and b* .

Yet the curves on pages 56-7 show a "clipped for human gamut" as-120 + 120 (yet PS is -127 to + 128)
Gernot Hoffmann, a colour scientist at Emden Uni in Germany, is a regular contributor to the Adobeforum (Photoshop)and I am sure if you posted your question (free registration)to the forum, he and others, would be only too pleased to help you with this.
http://www.adobe.com/support/forums/index.html

Regards
Mike H
OR
Owen Ransen
Oct 14, 2006
On Sat, 14 Oct 2006 09:45:04 +0100, "Mike Hyndman" wrote:

Gernot Hoffmann, a colour scientist at Emden Uni in Germany, is a regular contributor to the Adobeforum (Photoshop)and I am sure if you posted your question (free registration)to the forum, he and others, would be only too pleased to help you with this.
http://www.adobe.com/support/forums/index.html

Thanks for that link

Easy to use graphics effects:
http://www.ransen.com/

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