7D AF area selection

[mark_pierlot]

<p>I took my new 7D out for a spin yesterday, and must say that I quite enjoyed it. I do have a question, however, about AF area selection.</p>

<p>I was manually selecting single AF points in spot AF mode while photographing my daughter in a playground, and found that the focus was a bit off. I'd focus on her face, but her jacket would be more in focus. (I was using One Shot and apertures of f/3.5-4, and getting my daughter to pose to minimize movement. I had also done some "testing" to rule out back or front focusing issues with the lens I was using.)</p>

<p>If I'd been using my 5DII or (now sold) 50D under these conditions, I would have focused with the center point, recomposing when necessary, and the focus would have been quite accurate.</p>

<p>I suspect that the problem is that I was using spot AF rather than standard single-point AF. Could any experienced 7D users please advise me here.</p>

[Andy Collins]

<p>I'd be interested in seeing what happens for you when you try standard single-point AF instead to see if it's an issue with your camera or lens, or if it's just a matter of getting more familiar with the camera itself. I don't often use Spot AF but normally use single point with assist from the surrounding AF points and find this to be my favorite setting. <strong>Keith Reeder</strong> or <strong>Puppy Face</strong> can probably answer your question much more helpfully than I can as they are 7D gurus with extensive knowledge of the camera. I do hope you enjoy the camera as I think it's one of Canon's finest, regardless of the endless "7D vs. Whatever Camera" threads that pop up every week.</p>

[mark_pierlot]

<blockquote>

<p>I'd be interested in seeing what happens for you when you try standard single-point AF instead to see if it's an issue with your camera or lens, or if it's just a matter of getting more familiar with the camera itself.</p>

</blockquote>

<p>Thanks, Andy. I'm definitely going to try another lens as well as standard single-point AF. I was using a newly acquired Tamron 17-50/2.8 non-VC, and am going to try my EF 24-70/2.8 II. I've heard that the Tamron suffers from focus shift, but I'm not sure that applies here.</p>

<p>I have read that because spot AF pinpoints the focus so precisely, it's hard to maintain it while handholding, which was what I was doing. I guess slight forward or backward motion could have thrown the focus off.</p>

<p>I do hope that Keith or Puppy Face sees this thread, and offers me some advice. It was Keith's endorsement of the 7D, as well as his astounding samples of highlight recovery, that finally convinced me to get a 7D.</p>

 

[PuppyDigs]

<p>I love spot AF mode on my 7D but it's not as reliable for general photography due the reduced target area. I use it for macro where I need to lock onto a detail. The normal sized AF point is so large it often locks onto a more contrasty detail behind or in front of the desired detail. However, I've found spot AF to be the most accurate of the AF modes as far as nailing exactly where you placed the sensor. If you're getting front or back focus consistently, there is something wrong either with the lens or the MA setting. I've not tried a Tamron lens but spot AF works great with all my Canon optics.</p>

<p>I found the expanded point mode works better for gently moving subjects.</p>

[jaydesi]

<p>I use spot AF most of the time to get focus exactly where it's needed, and any time it's off, it's my fault.</p>

<p>Another thing to consider, after all other things are ruled out, is using micro adjustment. Both the lens and camera may be to spec, but if they are slightly off in opposite directions, it could lead to missed focus. So try checking all possibilities first, but after that, try using a test chart and checking the focus if nothing helps.</p>

[mark_pierlot]

<p>Thanks, Peter and Jay.</p>

<p>I just reviewed some images I took with my 50D and the Tamron 17-50 (which is also a recent acquisition), and there's evidence of front focusing there, too. So this points to the lens as the culprit. I'm going to shoot some images tomorrow with the 7D and a different lens (the 24-70/2.8 L II) to test this hypothesis.</p>

<p>I'll keep you posted...</p>

[mark_pierlot]

<p>I've now done some focus testing with my 7D and 24-70, and have obtained very sharp results, even at 100%. So I guess the culprit was the Tamron 17-50, after all.</p>

<p>I think I'm going to enjoy using the 7D!</p>