Image Engineering digital camera tests white paper
In order to anticipate a major aspect: measuring specific image quality aspects helps a lot in characterizing a camera but these measurements always have to be related to the real world images and there are numerous aspects which we will never be able to measure. So it is impossible to completely test a camera without taking pictures of natural scenes.
We at Image Engineering based our measurement procedures on the ISO standards which were already on their way at the time we built up the first test stand in 1997, and which served as a good starting point. In order to get a sufficient characterization of a digital camera, a couple of characteristic values seem to be mandatory and others may be recommended or optional.
The two characteristics which seem to be most important are to measure the OECF (opto electronic conversion function) and the resolution, but a few others belong to this group as well.