Originally posted by Ontarian50 What the OP is getting is bounce back off the sensor,
Or more likely off the well-coated surface of the front element of the lens.
Originally posted by Ontarian50 ...which is why you won't see it in the viewfinder before the shot
Mmmmm . . . if it's a reflection off the sensor it's present on the
back surface of a lens element and therefore observable in the VF . . . if you're looking for it.
A primary characteristic of Di coatings is that they're also applied to the
rear surface(s) of lens elements to reduce those pesky internal reflections.
Personally, I love filters of all types. The
empty rings are useful for many things including modular, stackable hoods and filter thread protection.