5D Mark III: 3 Bad AF Points

[jblake]

Hello I just got my new 5DM3 about 4 days ago. It has worked perfectly for me in this short period of time. But this morning I was checking out the accuracy of the outer AF points and all were focusing accurately until I got to the three top 5.6 cross points; if you orientate the camera into the landscape position, it would be the top three points, in the center block of 21, as seen through the viewfinder.

Every once in a while one of the three would attempt to focus, it would appear to move in incrementally a couple of mm at a time and then give up. This would take place say 1 out of 5 attempts, the other two rarely did anything. I tried removing the battery, changing the battery, and use a different lens, but nothing worked.

I have a 24-105L, 70-200 2.8 II and a Sigma 85 1.4. Of course rotating the camera to portrait position made no difference. My luck, both PMI Digital (who I purchased it through) and CPS are closed until Monday morning. I think I will call CPS in Newport News, VA first to see if they would want to take a look at this problem first or try to do an exchange with PMI. Yes, the solution is rather straight forward, but I thought I would post this just out of frustration with a brand new camera.

 

[klickflip]

Similarly I've been noticing some problems with my 5D III on outer points sometimes and sometimes even the centre points when using 85L. It seems to be out when its confirmed focus fine. Often 1 out of 4 are soft in controlled environments using one shot.. I need to do a full test to find out more. But it could be slight quirkyness of these two lenses especially when shot wide open.

Surprisingly I was doing a job the other day using 50L and photographing clothes on a dummy in the studio. So everything was static and tripod'd and shot at F7 with fastish duration studio flash so I was surprised when using the outer focus points the focus was off (seemed to be front focusing), not mentally but just a bit and when using centre point is was spot on 60% of the time but had to shoot 3 shots to make sure I have a perfectly sharp frame, there's a slight difference between all the shots, all are acceptably sharp but but 1 out the three would always be outstandly fully sharp.

Does anyone else notice this ? And whats the best way to test points vs lens. I did a quick AMFA on my 50L and 85L on the centre point recently and they needed +3 to 5 on a test subject about 2m away but then think that it may have focusing at made other distances worse...

Should AMFA compensate across the focus distance range or are you optimising it for the distance you test & recal it for?

 

[jonathan7007]

jblake,
You were right to test a lot in the first few days. I strongly urge you to be hair-trigger ready to exchange it if Canon Tech guys cannot point out something in your settings that immediately and consistently makes it respond as you would expect. Err to the side of caution: exchange is safest.

I took delivery of my 5D3 on the way out of town for long trip that was focused on daughter's graduation and interstate college/apartment move so was distracted (read: stupid) about aggressive testing and I now have a somewhat limited body in certain focusing challenges. I did speak to Canon a bunch and even sent in the body and lens and got a terse "Cannot reproduce problem." answer back. Canon Techs, trying to be helpful, were full of (sometime conflicting) suggestions but I should have sent it back despite the hassle of my at-the-time-6,000-mile distance from dealer.

This experience has made me hesitant to buy another... and I need another (third) body now.

 

[jonathan7007]

Kickflip:
About Reikan or other focus tests: I believe that YES you are adjusting for that distance you chose for testing. It makes testing the long lenses more challenging as they really should be tested outdoors. (wind, earthquakes, etc., and issue.) Reikan suggests 50X the focal length if I remember correctly. Others chime in if I have this wrong; Reikan does tell you that the focus mechanism will not always hit the same point. And the testing they do "de-focuses" the lens between test exposures so the motor is exercised to go after the "spot" at which you are pointing.

 

[jblake]

Re: 5D Mark III: 3 Bad AF Points "Update"

After 9 long days I have been reunited with my 5D3. CPS at Newport News, Va did confirm that the AF points that I claimed to be defective were in fact not focusing properly. CPS replaced the mirror box assembly/AF sensor as documented in the invoice. All AF points do auto-focus correctly now. Out of the first 13 days of ownership, I have only been able to use my camera for the first 4 days; time to make up for lost time.

 

[tpatana]

Story with a happy ending. My favorite type of a story.

I never tested my 5D3 that much, I guess I should.

 

[mrmarks]

After reading this, I will check my outer AF points too. I had my 5D3 cmos sensor changed under warranty by Canon recently due to unremovable dirt inside the sensor filter. One wonders what is happening with Canon QC.