Its not the camera thats doing it, its the lens. What you're seeing is the aperture ring (it shows up with some lenses at higher F stops - in other words when the hole you're shooting through is smaller the edges can show up on your shot sometimes.) Cool effect, I actually artificially add it to my shots after the fact some times:
ps: did you happen to get any shots of me on this green kawi? I was going ultra slow so probably an easy target
Bookmarks