> Your first paragraph made me think of harmonics and difference tones in > music. BTW, what's the CIE standard color space? You can find thousands of pages that mention or describe this on the Internet. Google gave me a bunch including the following which seem rather good 'pages explaining the scientific method behind measuring and describing human color perception: http://hyperphysics.phy-astr.gsu.edu/hbase/vision/… http://hf.faa.gov/Webtraining/VisualDisplays/… http://photography.about.com/library/weekly/… http://www.photo.net/photo/edscott/vis00020.htm http://escience.anu.edu.au/lecture/cg/… --Lee Poulsen Pasadena area, California, USDA Zone 9-10On Jan 23, 2004, at 4:36 PM, Jim McKenney wrote: