Canon 7D vs Nikon D700 Auto Focus

[colm boran]

<p>In this recent <a href="../canon-eos-digital-camera-forum/00XwUf">post</a>, I mentioned the inconsistency that I have been experiencing with Canon 7D Auto Focus. My friend that returned his 7D due to focus inconsistency bought a Nikon D700 instead, and we were curious to see if it could focus more consistently on static subjects. He came by the other day and we shot a few frames. </p>

<p>This quick study is far from conclusive, but as you can see in the images <a href="http://www.number6photo.com/Canon7DvsNikonD700/index.html">here</a>, despite using center AF detector aimed straight at the middle of the cylinder, and using single-point AF (set to Spot AF, for pin-point focusing), the Canon 7D seemed to be back focusing on the rope cylinder for some of the images. You can tell because the edges of the cylinder (farther away from the camera) appear more in focus than the middle of the cylinder. As you can see, the 7D eventually nailed the focus on the fourth frame. </p>

<p>The Nikon D700 is a full-frame camera with only 12 MP, so the magnification of the rope isn't as great in the cropped images. It appears to hit the focus in every frame identically, and appears to be focused on the front of the cylinder. But is it really better focused? Or does the full-frame combined with the fewer pixels make it too hard to tell? </p>

<p>Setup: similar to the previous study, each camera was mounted on the same tripod, mirror locked-up, shot with self-timer, at 200mm focal length at f/4. Between each frame, we manually de-focused the lens, alternating between front- and back-focus points. </p>

<p> </p>

[tallplumphotography]

<p>Wouldn't the full-frame make any focus inconsistencies more obvious rather than less obvious than Canon's APS-C?<br>

Perhaps repeating your test with a chart to test front-and back-focusing would make comparison easier? I've used this one to diagnose lenses in the past: http://focustestchart.com/chart.html</p>