"preferred white point" was "The Mystery of Adaptation"

Danny Rich wrote

>I personally believe that the
>human observer has not only certain preferred memory colors but also a
>preferred memory white point which is approximately D65.  But I have no
>objective data on this only my and other color engineer's anecdotal
>evidence.
>
>Danny Rich
>


Danny,
I am loath to disagree with you, but let me add some anecdotal experience that
is vrey contrary to your outlook.  

When Tailored Lighting developed SoLux, we first came out with a bulb to
simulate direct sunlight color temperature (D50 or "Source B" which are fairly
close to each other).   That bulb, the 4700K Solux, has technical applications
as an excellent D50 simulator, but it was NOT well recieved in the art or
interior lighting markets because it was too "cold."  

So, we did some tests with a system that allowed us to gradually shift a smooth
Spectral Power Distribution (SPD) (while maintaining the intensity) so that we
could change the color temperature continously from 2800K to about 5000K.  We
took this system and tested it on some of the finest art in the world at the
National Gallery of Art.  

The result -- we found that around 3500K (with a smooth SPD) was the
"preferred" place to view art.  Since then we have found that it is also
preferred when compared to 4100K or standard halogen (about 3000K) for
illuminating interiors.  It seems to be very close to the light that occurs at
the "magic hour" during the day.  
That is why we developed the 3500K SoLux bulb which has been well recieved by
the art community.  Note: we have noted a preference shift to a cooler light
for artwork that is predominated by cooler colors (usually more modern works) -
up to about 4100K.  

We also believe that intensity affects this preferred light.  The higher the
intensity, the higher the preferred color temperature.   This seems to go along
with what Kruithof found years ago.  

Based on this work, I do not think that D65 would ever be "preferred" by very
many people.   I believe it would be seen as very "cold."

Just thought you might want to add our experience  to your "anecdotal"
experience.

Phil Bradfield, Ph. D.
VP-Tailored Lighting Inc.
Where SoLux was invented
www.solux.net
800-254-4487
phil AT solux DOT net