[Radiance-general] measuring color

[Lars O. Grobe]

> Yes, it is true that the chromaticities are known for those colours, 
> BUT this is under the assumption of a certain illumination source. 
> Will you have that same illumination source? Probably not.

Hi!

The trick is to use the SAME illumination source ;-) I have done a 
number of such measurements in archeological context by simply taking a 
camera and the color chart to the site. The method that is described in 
Rendering with Radiance requires some installation (I think it was 
developed to measure material values in some kind of "studio"). I did 
it a bit simpler: one person holds the chart next to the material, I 
take a photo of the surface with the chart. As long as there is no 
variation of lighting over the area (no highlights etc) this seams to 
be a rather comfortable way, and I think for me it was accurate enough. 
Of course the chart should not cover the 5% of the area at the border - 
the chances that it is in a different lighting situation is to high 
than.

However, any expensive hardware is fun - and maybe you can even compare 
the results of the color chart way and the hardware way. I would be 
interested in that ;-)

CU Lars.
--
Lars O. Grobe
grobe at gmx.net