We have a Sony HDW-730S HDCAM camera with a Canon Lens. Lately, we've had an issue with what we originally thought was a backfocus issue but more testing seems to point that it isn't the backfocus.

It has characteristics of BF issues only in that it doesn’t hold focus. And when I say it’s “not holding focus”, it’s not your traditional “out of focus” look. It’s more like an slight but ugly, smearing that to the average eye would just be described as “soft” or “out of focus”. The wider the lens goes, the camera produces some sort of smearing when the iris is wide open. When this happens, it’s impossible to get a sharp picture even on a wide shot. It sharpens up the iris close. I checked the backfocus as the iris was wide open, and it was actually impossible to get a totally sharp picture after I returned to a wide shot from a telephoto. It was all that slightly smeared, blurry look. When I iris down a bit (on the darker side), I can confirm that the BF is set correctly. The extender dial is on 1x mode

Any ideas? Thanks