I'm hoping someone can shed some light on this issue. When I stop down any of my lenses past about f/4.0 I start to see a smudge that gets more pronounced the more I stop down. I don't usually stop down much, so I didn't notice this for a while.
The other day, I was shooting in bright sunlight, and so I stopped down the lens and started seeing this smudge.
I've cleaned the sensor three times and cannot see it at all when I shine a light in and look at the sensor. It happens at every ISO and shutter angle setting.
Anyone have any ideas??