Update (Nov 17, 2003)

> -----Original Message-----
> From: Mitchell N Charity [mailto:mcharity@vendian.org]
> Sent: Monday, November 17, 2003 10:07 PM
> To: efg2@efg2.com
> Subject: Color Reference Library feedback - specrend updated
>
> Your Color Reference Library pages
. . .
> mention specrend
>   Colour Rendering of Spectra
>   http://www.fourmilab.ch/documents/specrend/
> along with my 2001 email caution describing a problem with it.
>   http://www.efg2.com/Lab/Library/Color/MitchellNCharityColorNote.txt
>   (the Chromaticity.htm link to it is broken)
>
> Specrend's author reports the software has been fixed (as of March 9th,
> 2003).
> The webpage's chromaticity diagrams have not been updated however.
>
> Fyi.
>
> Given the number of older specrend.c's already out there, I'm not sure
> whether removing the caution at this time is a good idea or not.
> The webpage doesn't mention there was a problem (the C source does).
> You might add a note to MitchellNCharityColorNote.txt and leave it for
> a year or two.
>
> Thank you again for maintaining a wonderful resource.
> How are your funding challenges working out?
> Mitchell Charity

==========================================================================

From: "Mitchell N Charity" <mcharity@lcs.mit.edu>
To: <efg2@efg2.com>
Subject: Color Library Feedback - caveat on specrend's excellence
Date: Friday, November 30, 2001 16:49

I think I already mentioned this, but just in case...

I was pointing someone at your
  http://www.efg2.com/Lab/Library/Color/AndComputers.htm#FalseColors
(thanks again for running a delightful resource)
and noticed this entry

  Colour Rendering of Spectra (excellent article)
  www.fourmilab.ch/documents/specrend

While indeed a nice article, I some time ago realized, after much
puzzlement, that spectrend (web page and C program) had mishandled the
XYZ to RGB conversion by ignoring the location of the whitepoint.
This is most easily seen on the web page, where the xy chromaticity
diagrams have the "+ W" white point lable in one place, and the actual
white points in quite another. :)

I discussed this a bit on
  What color is a blackbody? - some pixel rgb values
  http://www.vendian.org/mncharity/dir3/blackbody/
and it's
  Different blackbody colors on the web
  http://www.vendian.org/mncharity/dir3/blackbody/different.html

Thanks again,
Mitchell Charity