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July 1999

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1999.07.19 12:53 "White point in CIELab TIFF files", by Martin Bailey
1999.07.19 14:12 "Re: White point in CIELab TIFF files", by Martí María
1999.07.19 16:03 "Re: White point in CIELab TIFF files", by Martin Bailey

1999.07.19 14:12 "Re: White point in CIELab TIFF files", by Martí María

> 
> The TIFF 6 spec is more than a little vague about what white point should
> be used for L*a*b* images, and there's no specified tag to put that data
> into the file.
> 

There is a tag to store White point, the tag is:

	Tag  = 318 (13Eh)
	Type = RATIONAL
	N     = 2

The chromacity of the white point of the image. This is the chromacity when
each of the primaries has its ReferenceWhite value.
The value is described using the 1931 CIE xy chromacity diagram and only the
chromacity is specified.

TIFF 6.0 specification has a "Section23: CIE L*a*b* images" where it says
that "White point : does not apply" but
I have seen several TIFF whith photometric = CIELAB and white point
specified as D50 in this tag.

Hope this helps

Marti Maria
ICR S.L.