Lesson learned: Keep all your glass clean
This weekend I was having a terrible time with my EVF. Peaking confirmed focus but the scene looked fuzzy, flat and dull. I'd lower the camera and bring it back up again and the scene would clear up and I didn't touch anything. At least the photos were turning out OK.
"Oh crap," I was thinking, "my A77 EVF has been knocked out of whack somehow. Here comes a fat repair bill." Despair ruled my day.
Tonight I took a close look at the EVF window. That little glass window you put your eye up to.
It was filthy. It's a wonder I didn't get some kind of eye infection looking through all that junk. There were a few semi-clean spots left so that explains why the scene would sometimes be clear or fuzzy and dull. I cleaned it with a cotton swab and some lens cleaner.
Holy Cow! It's like a brand spanking new camera!
So take a look at your viewfinder window (both EVF & OVF users can benefit from this) and see if it's dirty. Clean it if it is.