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New Contributor
Posts: 4
Registered: ‎06-16-2013

5D Mark III Phase Detect AF Failure

I am experiencing a bizarre AF problem with my two month old 5D Mark III. It has worked fine until recently, when all of a sudden it would not autofocus at all, with any of my Canon lenses, unless I switched to LiveView. Switching a given lens to my 7DM2 and trying the same scene would always result in perfect AF, so the problem seems to be in the Phase Detection AF system. Clearing all camera settings to the factory defaults did not fix this either. The problem exists in all AF and drive modes, but only with Phase Detection AF.  Live View AF always works in my tests where Phase Detect fails. Changing AF points and AF point expansions did not solve the problem.

 

I returned the 5DM3 to Canon Factory Service for in-warranty repair (after paying $34 shipping and insurance), and just received the camera back. I am experiencing the same AF failure!! Canon EOS Tech Support has submitted a request for me to receive a shipping label to again return the camera to Canon, but I'm told they won't entertain a replacement camera until Canon has attempted three repairs unsuccessfully.

 

Has anyone else experienced a similar problem? My searches don't turn up much.

Thanks for your advice!

VIP
Posts: 8,065
Registered: ‎08-13-2015

Re: 5D Mark III Phase Detect AF Failure

I'd say work with the Repair Department.  They seem to have a good reputaiton that they want to preserve.  I'd think the last thing they'd want is someone buying one of their professional grade cameras and getting bad service.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Reputable Contributor
Posts: 744
Registered: ‎11-14-2012

Re: 5D Mark III Phase Detect AF Failure

Just a thought. Dust at the AF module? http://www.dpreview.com/forums/thread/1973086#forum-post-23136302
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New Contributor
Posts: 4
Registered: ‎06-16-2013

Re: 5D Mark III Phase Detect AF Failure

Thanks for your comments. Canon Repair stated that they replaced the AF assembly, but the exact failure is still occurring. However, I have determined that the failures appear to be highly correlated with temperature. When the camera has been in temperatures of 40-50 F for a few hours, the failures occur. When it is warmed up to around 65 F or more, it works fine. I'm beginning to think it is an electrical problem caused by temperature-induced contraction and expansion. Pretty bizarre. 

Hoping to get the shipping label from Canon today to send it back again. Thankfully I have my 7D Mark II to use, along with an old 1D Mark 3 that I keep as a spare.

VIP
Posts: 8,065
Registered: ‎08-13-2015

Re: 5D Mark III Phase Detect AF Failure

Lithium-Ion batteries are supposed to be far less vulnerable to low temperatures that NiCad batteries.  You could chill down a NiCad, and it would measure almost zero volts.  Warm it back up, and it would measure fully charged.

 

Nevertheless, I would not allow my camera to exposed or stored at those temperatures for too long of a period of time.  The camera itself is only rated down to 32 degrees F, if I'm not mistaken.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
New Contributor
Posts: 4
Registered: ‎06-16-2013

Re: 5D Mark III Phase Detect AF Failure

A world of difference between 32 degrees and 45-50 degrees. But this $2500 camera first failed in the middle of an excursion photographing wild Whooping Cranes in 40 degree air temperature. My 7D Mark 2 was flawless, as was my friends 70D, and several people were shooting with their point-and-shoot megazooms with no proiblem. I've shot polar bears in the Arctic and penguins in the Antarctic with an old 40D with absolutely no focus problems whatsoever. This failure under such mild conditions is an obvious defect, that hopefully will get fixed on the second attempt,.

New Contributor
Posts: 4
Registered: ‎06-16-2013

Re: 5D Mark III Phase Detect AF Failure

Just got word that my 5D3 has been repaired for the second time, and was shipped today. They say that the Mirror Box Assembly was replaced. I googled Canon Mirror Box Assembly Problems and found a bunch of reports of 1DX problems with AF due to a defect in the mirror box assembly, and supposedly this was an issue that occurred more in colder weather. Would be interested to know if perhaps this may be the same issue arising in the 5D3. Will report back whether the problem is finally fixed.

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