[Radiance-general] measuring color

[Jack de Valpine]

Hi Genevieve,

There are a couple of options that I can think of off hand:

   1. Color Checker and Digital Camera - using the techniques that are
      outlined in Rendering with Radiance, you can use the Color Checker
      Chart from Gretag Macbeth and a digital camera to sample color and
      reflectance. The color checker is an accurate set of color samples
      with known measured reflectances and chromaticity coordinates. It
      can be used to calibrate color/reflectance information that is
      acquired through a device such as a scanner, digital camera, or
      even a regular old film camera. I think used correctly the results
      can be within +or- 10%. We have used this method with reasonable
      success on a variety of materials. This is a very economically
      method (~$100 for color checker plus cost of sampling device)
   2. Handheld Spectrophotometer - there are a variety of options out
      there for hand held spectrophotometers. I believe that Gretag
      Macbeth has several. These will likely be more accurate than the
      above and cost a lot more. I think when I last looked into this (5
      or more years ago) such a device cost ~$5,000 and did not include
      the software necessary for operation. I have not had the
      opportunity to use one yet.

Regards,

-Jack de Valpine

genevieve lucet wrote:

> Hi,
> In order to define colors for radiance models I'm looking for an 
> instrument to measure the colors of walls and of mural paintings of 
> archaeological sites. It should be portable, working with batteries 
> and non destructive to the material.  (max. price, $5000 US)
> Any recommendation?
>
> genevieve lucet
>
>
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-- 
#	John E. de Valpine
#	president
#
#	visarc incorporated
#	http://www.visarc.com
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#	channeling technology for superior design and construction

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