For the past few months, I’ve been having some serious focus issues with the Canon 5D2. It’s just not consistent. I can take one photo and it’ll be in focus, but the one just following it (less than a 25th of a second later) will be front focus and the kids’ shoes will be sharp, but not their faces. I shot a session a few nights ago that I counted only 22 in focus out of 250 shots I took. The rest are totally unusable and the session will have to be re-shot, costing me more time and money. It’s been driving me CRAZY, making me think I’d lost my touch or was seriously having issues with the learning curve. A few days ago, I put in “5dII focus issues” into Google and came back with a bunch of people who were having the exact same issues as me. I set the micro-adjustments in the camera and thought I had it all worked out, but upon more testing today, it proves not.

http://www.kenrockwell.com/canon/5d-mk-ii.htm
“Trying to photograph my wiggly toddler in low light with a 50mm f1.4 lens, the 5D Mark II and EF 50mm f/1.4 USM lens combo rarely gives me an in-focus shot at f/1.4 and f/2, while the Nikon D3 and D700 and old 50mm f/1.4 AF-D lens nail it perfectly almost every time. The Nikons have some sort of magic facial recognition, which comes from knowing 1.) the focused distance, 2.) having a color meter which reads 1,005 segments and 3.) having 51 AF segments, and 4.) knowing what to do with all this information, while the Canon 5D Mark II is clueless. The 5D Mark II has only a 35 segment, back-and-white meter, only 9 AF sensors, and no clue about subject distance.
I’m serious: the 5D Mark stinks for kid photography, while the Nikons rule. Of course even the old 5D is better or nature and landscapes that hold still. If you’re photographing things that won’t hold still for you, the Nikon D700 is worlds better. “

http://www.kenrockwell.com/nikon/d700.htm
“The D700 wins for just about everything, especially action and taking pictures of your friends, family and kids. The D700 has superior autofocus performance over the Canon 5D Mark II. The 5D Mark II’s AF system is inferior for photographing moving kids in dim light. All my D700 shots made with a 50mm f/1.4 indoors are just about perfect, most of my 5D Mark II shots made with a 50/1.4 USM just can’t nail the focus because the 5D Mark II lacks the face recognition of the D700. The D700 magically focuses on a moving kid’s nearest eye, while the 5D Mark II usually mis-focusses on his shirt, sleeve or background. At f/2, depth of field is so narrow that most of my 5D Mark II photos are useless for moving kids. Who needs 21MP if they’re out of focus? “

http://www.dpreview.com/reviews/canoneos5dmarkii/page40.asp
“So while the 5D Mark II would never be mistaken as a camera aimed at sports or action photographers (thanks to its rather pedestrian AF performance and overall shooting performance),”

http://www.kareldonk.com/karel/2009/02/09/canon-eos-5d-mark-ii-not-worth-it-save-your-money/
“Update 02/09/2009: In the mean time some more examples have been posted of the 5D Mark II focus issues. The fashion shooter I mentioned above, who had trouble getting his 5D Mark II to focus properly got another 5D Mark II body, and apparently he had the same issues with that one. Now he has decided to NOT use the 5D Mark II AT ALL. Here’s what he had to say:” I’ve come to the conclusion that the 5Deux has A.D.D. Sometimes it focuses very well. Other times, it’s slightly disappointing compared to results from the old 5D. I know the 5Deux can focus well, because I’ve
got proof, it just doesn’t focus well ALL of the time, which is annoying. I’ve seen other photographers say that they’ve had similar results, so I guess this is pretty common among 5Deux owners. This latest AF issue follows on the heels of a Live View exposure problem with the Canon 5D Mark II. I think it’s fair so say that with 3 professional camera models with issues, this firmly establishes Canon as having a track record of not testing products adequately. And at the
cost of customer time, hassle, and perhaps money.”

The 5D2 is under warranty, but they won’t send out labels. I mean, I am a pro photographer. I know my gear. Hell, I just wrote an article for Canon about how to do what I do! I just paid $50 to ship my brand new 5dII back to Canon for repair for autofocus issues. I should NOT have to PAY to send them back something that should have never passed quality control in the first place. I’m shocked that this isn’t even an acknowledged issue since there are tons of people online with the same problem.

I sent the links above to Canon in an email as well as my issues and got this back:

“Thank you for contacting Canon product support.  We value you as a Canon customer and appreciate the opportunity to assist you.  We are sorry to hear of the trouble that you have had focusing with your 5D Mark II.
We haven’t found any focus issues with the EOS 5D Mark II.
Your comments about the 5D Mark II noted and will be passed along to the appropriate party. Thank you for taking the time to write.  Please let us know if we can be of any further assistance with your 5D Mark II.”

I’ve never been so close to jumping ship and going with Nikon, and if the 5DII comes back from Canon with the same issues, I seriously be looking hard at the D700.