Just as a follow up I did the following experiment:
1) I grabbed the ColorChecker spreadsheet summaries (using the Lab version)
from Bruce Lindbloom:
http://www.brucelindbloom.com/index.html?ColorCheckerRGB.html
2) I converted the D50 Lab coordinates to XYZ (these do not totally agree with
the values from the ColorChecker Calculator but it should be OK for this
purpose)
3) I computed the adaptation matrix from D50 to D65 using both the ICC matrix
and Lam's matrix
4) Then I converted back to Lab and compared the result with the values using
the D65 source.
To summarize the results I got the following differences (DeltaE CIE76 for
simplicity) :
ICC: Lam:
--------------------------------
Median: 0.89 1.60
Max: 3.14 6.40
RMS: 1.31 2.40
So I am completely satisfied that the ICC specification got it right after all.
Sorry for the noise.
Regards,
Esben H-R Myosotis
Software Engineer
Phase One
> -----Original Message-----
> From: marti.ma...@littlecms.com [mailto:marti.ma...@littlecms.com]
> Sent: 31. oktober 2014 02:57
> To: Esben Høgh-Rasmussen Myosotis
> Cc: Lcms-user@lists.sourceforge.net
> Subject: Re: [Lcms-user] Chromatic adaptation using the Bradford method
>
>
> Ok, I've checked this with Phil Green, the ICC technical secretary and
> with Ronnie Luo, who most of you already know.
>
> The typo is in Lam's paper. The reference Phil gives is Hunt, R. W. G.
> 'Reversing the Bradford chromatic adaptation transform', Colour Research
> and Application 22 pp355-356, and this gives the same value as that used
> in the ICC spec. Ronnie corroborates the coefficients in the last row
> should add to 1.0.
>
> Regards
> Marti
>
>
> Quoting marti.ma...@littlecms.com:
>
> > Hi,
> >
> > Thanks for reporting, I am bringing this issue to the ICC.
> >
> > Regards
> > Marti
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