I would have thought that those who tend to like confusing backgrounds might appreciate catadioptrics just because of this.

I gave away my Canon 500 to a friend who thought it might be useful outside the visible spectrum. Riddance due to a tendency to a hotspot which the Leitz (Minolta) equivalent did not have (a possible explanation is that the surgery needed to remove the FL mount and fit a mount for a longer back focus did upset its internal baffling, so it may not have been a design fault). Apart from the peculiar Perkin Elmer mirror lens all my catadioptrics stem from Chiuoda kogakus avatars

p.