Good for imaging, unsuitable for measurement (Score 3, Insightful)

Consumer imaging devices are great if what you want to record are spatial patterns of light in an image or over time. But if you need to record absolute light values, or measure differences within a still image, or compare values over time, you will need a scientific measuring device capable of maintaining a calibrated black level as well as a known response to light. Consumer scanners typically only maintain a calibration within a single scan cycle, then recalibrate for the next scan, in order to give consumers the best digitization for each individual target. Consumer photo and video CCDs let the black level 'float' over time so as to give the best overall exposure at any given instant. These design features make consumer equipment useless as measurement devices, but ideal as pattern recorders.