Canon 24-70 f2.8L focus issue

I've had my 24-70 for several years and generally more than once every time I use it I have a focus issue I just can't figure out. It's nearly always sharp, but occasionally it will just miss the focus on everything. It's no different on my 20D, 40D or 7D. Here are two pretty typical results. One in focus, one not, taken 3 seconds apart, no one moving. In the one that's out of focus, there's nothing in focus, not the people, background, nothing. I'd send it to Canon for calibration or testing, but don't think they'll find anything. Anybody got any ideas?

http://tnicol.net/potn​/20110326_170322.jpg

http://tnicol.net/potn​/20110326_170325.jpg

Thanks.

It's really hard to see as the images are a little too small to tell...however, I think in the second image, the gentleman's hands to camera right is in focus. Can you link some larger images? I'd be curious to see these again. I've had the same issues in the past, but once I put mine on my 1D Mark III and/or 1D Mark IV, I haven't seen the issue.

I also notice that you are shooting at 1/125 @ f/4. While you would think that is a fairly good shutter speed, I believe the slightest bit of movement will still amplify to the point that your shots will come out a tad soft...just my opinion though.

Edit: It appears that the hand is not in focus after all. At this time, I would have to say it may be a little camera shake or you have a "soft" copy of the 24-70.

Thanks for looking. Larger versions are now up using the same links. I thought the same think looking at the hands (both camera right and left), but looking more closely they're out of focus in the bad one too.

I've thought about camera shake too, but it happens on a tripod too, though this for this one I didn't use a tripod.

I trust you were using center point focusing with the 7D? Also, are you using any back buttons to focus or are you using half shutter release to focus? I ask because the more I look at the larger image, the more I see the gentleman left (camera right) sleeve (middle of forearm) that appears to be in focus. If you are using the shutter button to focus, I'm thinking the next time you depressed the shutter release, it refocused onto the sleeve.

I don't use any back buttons, just the half-shutter release, and the focus was center point. If you look at the buttons on the jacket of the guy at camera right, they're out of focus too at least more so than on the one that's in focus. Even if I'd focused on some other part of the group besides the center, it should be better than that. If you look at the one in focus, even the background is fair so there's plenty of depth of field.

Yeah...looking at the one that is in focus, his buttons are a little soft so I believe you are correct. I think at this point you either send it in for calibration or you MA it to fit your 7D. In the mean time, I hope someone with more experience will come along and help you out. Good luck!!

Can you copy/paste all the image info? Let's start there.

Can not offer any help here other than to say I get exactly the same issue on my 5d (ii) with the canon 24 -105 L series Lens. Tripod mounted focus on manual, IS switched off taking a series of shots, in a studio spaced about 15 seconds apart one will be out of focus two or three either side are spot on.

James

You're not resting the focus ring on your hand are you? Could easily throw it OOF post AF if you're not careful.

Quite a few owners of this Lens have experienced focusing issues with their 24-70 lens. Nothing Canon can't correct as they always seem to report back that its perfect when returned.

keith breazeal wrote in post #12142367
Can you copy/paste all the image info? Let's start there.

Keith, exif info should still be with the images, but basically 125@f4, iso 400, on-camera flash fired. Thanks for any help you might offer.

Tsmith wrote in post #12143225
Quite a few owners of this Lens have experienced focusing issues with their 24-70 lens. Nothing Canon can't correct as they always seem to report back that its perfect when returned.

TSmith...so you're saying you've heard of people with this issue that have had it corrected when sent to Canon? I'd be willing to try that if I thought it would work. I just fear it's so random and intermittent they might not find anything. I appreciate your thoughts.

phreeky wrote in post #12143216
You're not resting the focus ring on your hand are you? Could easily throw it OOF post AF if you're not careful.

I did think of that quite a while back, but don't think I'm doing that. It's a good thought though.

JamesPhillip wrote in post #12142674
Can not offer any help here other than to say I get exactly the same issue on my 5d (ii) with the canon 24 -105 L series Lens. Tripod mounted focus on manual, IS switched off taking a series of shots, in a studio spaced about 15 seconds apart one will be out of focus two or three either side are spot on.

James

James, that only discourages me because I've thought about buying a 24-105, not just for this problem, but for the slightly longer reach and IS too. Maybe I'll save my money!