I've had a 24-70 for a couple of years. Bought it new and have been delighted with the IQ. Only recently, though, did I notice that it front focuses by quite a bit at ~35 and back focuses at least as much at 24. I come to find this is a common issue with these lenses and I have arranged for Canon service (which they will hopefully perform at no cost).
It got me looking harder at how my other zooms focus. My 70-200 is flawless, but my brand new and very pricey 16-35 II has the same issue as the 24-70, back focusing considerably at the wide end.
So I guess my question is whether or not this inconsistency is to be expected. Should I expect precise focus across the range or is it reasonable that lenses focus more eratically at the wide end?
