Originally posted by Mothballs I get good results with a flat element cosina 55mm f1.4. get interesting light rings sometimes.
The Tamron 90mm 2.5 however, that gives the purple center reflection.
i have a couple of those lenses, i've never seen any sensor reflection, neither on the k10d nor the a7r.
sensor reflections are often caused by the camera body, the a7 problem for example, has been well documented even on this forum, with multiple modern lenses... it usually happened at night, with longer exposures in particular.
sony fixed the issue with the a7ii, it does not have a sensor reflection problem.