Spent the day prepping for an assignment by checking my bodies and lenses; I don't want to discuss camera bodies right now but they are 3 different current flagship / top of the line models from one of the big 2, all with Aual with the ability to fine tune auto-focus performance. I tested focus using a LensAlign Pro, tripod mounted very carefully set up aligned and lit, and the target to sensor plane distance set to 25x the focal length of the lens being tested. Camera was also tripod mounted.
All of the lenses --save one -- tested fine at maximum (wide open) aperture on all ofthe bodies. By "fine" I mean that the auto-focus needed adjustment for each body /lens combination but nothing extreme.
The single partial exception to this was a 50mm f/1.4 on just one of the bodies. Based on careful examination, it looks like it would need an AF adjustment setting of a about +23 or +24 for that specific body /lens combination. In other words, this one lens on this specific body has greater back focus issues that the AF adjustment can't handle. On the second body it very slightly backfocuses requiring a +3 correction while on the third body another body it slightly front focuses.
Has anyone else ever seen this? A specific lens that doesn't want to focus well on just one body?
Tomorrow I plan to either rent or borrow another 50mm f/1.4 as a cross check but please chime in if you have had this problem.
Ellis Vener
http://www.ellisvener.com
