As i mentioned we decided to detect 0603 and 0805 case style Elements, and classify detected elements as Resistors or Capacitors. This was pretty hard, because you have to imagine, that if you are only looking onto a black and white image, some 0603 resistors can not be differenced from pads of unequipped parts. After hours of hard work the results can be shown:

For that shown whole PCB we got very good results:

correct positives: 109 (out of 123)
false positives:      18
false negatives:    14
positive detection rate: 88,62%
precision:                             85,83%

Here a short comparison of the classification preformance to other Boards, where the results are not as good, but its still very impressive how good that works: