Can a consumer grade flat bed scanner be used as a colorimeter?
The general answer is no, but you can make a reasonable approximation if you know the characteristics of the material you are scanning. For example, if you are always scanning photographic prints that are made of the same three dyes, then it is possible to derive an accurate conversion from the scanner readings to XYZ values for that material. However, when you scan other materials, the conversion would not be accurate.