...monitor calibration tool? These spyder thingies have been around for quite a few years, and $149 is pretty cheap. There can't really be much electronics involved. A sensor of some sort. Maybe, if its fancy, a red, green, and blue LED as color references... Maybe... You already have a much more precise color sensor. I wonder, if you'd generate a neutral gradient in Photoshop, and then photograph it with your Canon, and then compair the two... Interesting mathematics. Think I'll go back and read that aim-dtp.net article a bit more carefully...