7D inconsistent focusing

Started Oct 5, 2013 | Discussions thread
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quantum mechanic
Forum MemberPosts: 85Gear list
7D inconsistent focusing
Oct 5, 2013

Hello. I want to share my recent frustrating AF experience with my 7D. I’ve had it for three years, and I was never quite happy with AF, it simply too often exhibited the tendency to front-focus. This was slightly dependent on the scenery and lighting conditions as well as on the lens used. I also tried MFA and focus charts, with no significant issues. I also sent once the camera to Canon, but they concluded its AF was within specs. I somewhat accepted the fact that in some situations the camera is not exactly reliable, and pursued no further actions.

This spring I’ve got the 5DIII, and my perception and expectations regarding AF notably changed, namely towards higher standards. The 5DIII really nails down the focus, even in poor conditions, and the amount of missed shots is very small (or is due to evident user error). I want to keep the 7D though as backup or for less secure situations, in which the risk of damage or theft is increased (e.g. for beach holidays). Also with my new lens lineup (16-35L, 24-105L, 24-70L II) I intend to sell my existing EF-S lenses.

Paring my 7D with the 24-70L II revealed particularly bad AF performance of the camera. Among the shots I took of a single scenery (my son playing) only about 20% were in acceptable focus, while the remaining 80% were front-focused. Very frustrating is that the focus miss is not uniform, but varies over a wide range of just barely in front to a complete miss. Hence it is probably not correctable by MFA. While the AF performance may somewhat depend on the scenery and lighting, the amount of misfocused images is unacceptably high even in good light. All in all, I can never tell in advance what result I can expect. Below is an example of my child playing; the focus was set to the right eye (as seen by photographer), but the focus clearly missed, as indicated by the arrows designating the area most in focus (single point AF, one shot, f/2.8, 1/400 sec., no recomposing, no fast and unpredicted movements of the subject):

In better light deviations from proper focus may be smaller and less frequent, but still at unacceptable level, front-focus affecting probably 50% of shots. Again, the most frustrating part is that rather than small but constant amount of front-focusing I usually get a wide range between proper focus and complete miss – all for the same scenery! However, back-focusing issues are extremely rare.

I’ve noticed similar problems with my 24-105 lens as well, albeit slightly less pronounced. In contrast to that, both the 24-70 and 24-105 operate flawlessly on my 5DIII.

I wonder if this AF issue could be treated and what kind of repair can work the problem out. Anybody here experienced something similar and how did he/she handle it? Should I better consider buying another APS-C camera (I’m tempted by the 70D due to its live-view AF performance as well as the articulated screen) than repairing the 7D?

 quantum mechanic's gear list:quantum mechanic's gear list
Canon EOS 7D Canon EOS 5D Mark III Canon EF 50mm f/1.4 USM Canon EF-S 10-22mm f/3.5-4.5 USM Canon EF-S 17-55mm f/2.8 IS USM +6 more
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