Hi, I have an old 70-200 mk 1 non is lens. I bought it used about 4 years ago. I dont know the lens' history. Anyhow, I was originally using it on a 7d mk1 with variable results. My tack sharp rate was as low as 30%. I did the usual focus tests but it would front focus, back focus and be spot on in a 5 shot series. Therefore I could not do the normal AFMA calibration. Any ideas why this might be?
Anyhow, my 7d died 4 months ago and I have been without a body until I bought a new 6d mk1 a couple of days ago. Not surprisingly, I have exactly the same issue. However, I noticed during testing, that if I manually set the focussing ring at the minimum focus distance, then tried t autofocus on something, say 20 feet away, the lens would move, but stop short of actually focussing and fail. I would then have to half press the shutter again for it to complete the focus successfully, albeit that it might or might not be tack sharp. So, it appears that it has to be fairly close to the focus range to focus in one go, or it stops short. Is this normal? I'm presuming not and that it should be able to focus from one extreme to the other in one go.
Thanks in advance for any replies.