Originally Posted by maestro
It was a quality one and when set to sharp then gave the same good picture as without it, just simply shifted the focus with a few metres.
Hard to say Andras what was going on. The good ones look the same as the bad ones, but of course a camera is not a rangefinder and just focuses accordingly. But if the lenses weren't totally flat, then you could see some distortion. The Leupold 50ft adaptor is such a shallow distortion it looks flat and can't even be ground on normal optical kit in the uk, it's that shallow.