@jkallmeyer, Hey Jack now I see the failure … yes you are absolutely right the distortion at the edge is quite high but the pics from Tynessa are not so bad and give me the feeling that there is a way to make them even better. I know that these set ups will not reach the level of a professional camera with special macro lens but we always have to think about the budget. I will try to make some testings with different models. Maybe I can figure out which one should be recommended and which one we can forget.
greets
Ronny