Auto Area AF Gone Wild

tiggy@mac.com

Pentax K-1000
Jan 20, 2014
484
159
Thetford, VT
www.ForestMetrix.com
I had a hiccup yesterday when I finally had the opportunity to shoot a wild snowy owl. It was on a flagpole, and when it took off, I changed from single point AF to Auto Area. This was a simple thumb press, as I have both hooked up to different back-button-focus buttons. I've used this setup for years with no issues.

And then the lens started doing a strange, repetitive, short-distance focus racking. Perhaps three or four shifts in direction per second.

I had to follow the owl with single point. I was able to swap to my backup camera (a 5d4 with identical settings) and that one worked fine.

After the owl incident, I switched lenses on the questionable camera, and it did the same focus racking thing. I did find I could get auto area AF to work on very high contrast subjects. But not with lower contrast subjects, such as a snowy owl against the sky, or the line of a room corner leading up to the ceiling. My backup camera did these things fine.

I first figured I just have some odd setting switched on, but I literally went through the entire menu system, and there isn't anything set differently between cameras.

Could it be that there's a foreign object on the focus sensor or something? Just curious if this sounds like an obvious case of something. Thanks. -tig
 

Valvebounce

EOS 5D SR
Apr 3, 2013
4,201
167
52
Isle of Wight
Hi tig.
Just a couple of thoughts, are they both on the same firmware?
Has either been updated from a previous firmware, if yes did you do the recommended reset?
Did you send this question to Canon support? They may have an answer if it is something on the AF sensor, or some other problem they have seen before.

Cheers, Graham.
 

Ian_of_glos

EOS RP
Jun 12, 2012
241
23
England
What is the lens you are using? Does it have the option to limit the focus range so it doesn't have to move a long way if it is unable to pick up a subject with good contrast?
Do you have the following option on your camera body - lens drive when AF impossible? Stupidly I set this to Off and then I found that then the autofocus stopped working completely.
 

tron

EOS 5D SR
Nov 8, 2011
4,012
319
Ian_of_glos said:
What is the lens you are using? Does it have the option to limit the focus range so it doesn't have to move a long way if it is unable to pick up a subject with good contrast?
Do you have the following option on your camera body - lens drive when AF impossible? Stupidly I set this to Off and then I found that then the autofocus stopped working completely.
It does but in that case you just help it by manual focusing (with the lens in AF mode) close to the correct point. Then when it is almost correct it kicks back in. You see the recomendations are indeed to set it to OFF.
 

Maximilian

The dark side - I've been there
Nov 7, 2013
2,549
350
Germany
Hi Tiggy and to all others!

Ian_of_glos said:
What is the lens you are using?
To me this is the most important information to solve this.
If your backup body worked fine just until you switched the lens from the "hickup" body that indicates that something happened here because of the interaction of body SW and this dedicated lens SW.

You should also do some tests with both bodies an other lenses to find out, if your AF settings are only to hiccup with this certain lens, or if this is now also happening with other lenses.
 

tiggy@mac.com

Pentax K-1000
Jan 20, 2014
484
159
Thetford, VT
www.ForestMetrix.com
Sent camera in to Canon.

They found sensor assembly misalignment.

Spent yesterday shooting the fixed body, and it worked great.

Canon CPS was fast, accurate and went above the call again. They found a budding problem with the top dial, so they replaced that to free. Sent it back Fedex for free, to where I am shooting.
 

Valvebounce

EOS 5D SR
Apr 3, 2013
4,201
167
52
Isle of Wight
Hi tig.
It is good that there was a real reason for this behaviour and that you were able to get it fixed, there is little worse than an intermittent fault that does not appear during a repair! It is great that they also remedied the top dial issue, the sad part is that you had these issues in the first place and both on the same body to boot.
The service sounds like it was above and beyond the required level.
Out of interest how old is the body that had the issues, was this a warranty repair?

Cheers, Graham.
 

tiggy@mac.com

Pentax K-1000
Jan 20, 2014
484
159
Thetford, VT
www.ForestMetrix.com
Valvebounce said:
Hi tig.
It is good that there was a real reason for this behaviour and that you were able to get it fixed, there is little worse than an intermittent fault that does not appear during a repair! It is great that they also remedied the top dial issue, the sad part is that you had these issues in the first place and both on the same body to boot.
The service sounds like it was above and beyond the required level.
Out of interest how old is the body that had the issues, was this a warranty repair?

Cheers, Graham.
The camera was one of the first off the production line. Has been VERY heavily used and knocked around, including being dropped on concrete on day 1.

This wasn't a warranty repair because it was many months out of warranty. That, and to make this problem, I think you have to do something to the camera that would constitute an attempted murder charge were it done to a person.

The surprising part is that the problem surfaced what must have been days/weeks/months after a jolt, rather than proximate to an actual bump. For this reason, I was almost sure it must be a setting or something I was doing.
 

Valvebounce

EOS 5D SR
Apr 3, 2013
4,201
167
52
Isle of Wight
Hi tig.
Ah it sounds like you have been proving just how sturdy these cameras are! ;D
Dropped on concrete on day 1, man that must have really annoyed you, I would have been kicking myself for days for that!
It does seem strange that the problem didn’t surface immediately after a blow, but had you used the AI Servo on a poor contrast target until that point, with all the other conditions too! Who knows why these things behave the way they do.
I’m glad you are not being prosecuted for attempted cameracide! ;D ;D

Cheers, Graham.

tiggy@mac.com said:
Valvebounce said:
Hi tig.
It is good that there was a real reason for this behaviour and that you were able to get it fixed, there is little worse than an intermittent fault that does not appear during a repair! It is great that they also remedied the top dial issue, the sad part is that you had these issues in the first place and both on the same body to boot.
The service sounds like it was above and beyond the required level.
Out of interest how old is the body that had the issues, was this a warranty repair?

Cheers, Graham.
The camera was one of the first off the production line. Has been VERY heavily used and knocked around, including being dropped on concrete on day 1.

This wasn't a warranty repair because it was many months out of warranty. That, and to make this problem, I think you have to do something to the camera that would constitute an attempted murder charge were it done to a person.

The surprising part is that the problem surfaced what must have been days/weeks/months after a jolt, rather than proximate to an actual bump. For this reason, I was almost sure it must be a setting or something I was doing.
 

Maximilian

The dark side - I've been there
Nov 7, 2013
2,549
350
Germany
tiggy@mac.com said:
Sent camera in to Canon.

They found sensor assembly misalignment.

Spent yesterday shooting the fixed body, and it worked great.

Canon CPS was fast, accurate and went above the call again. They found a budding problem with the top dial, so they replaced that to free. Sent it back Fedex for free, to where I am shooting.
Thank you for that update. And good to hear, that the issue could be fixed.

Did I get that right?
You sent in both bodies and both hat the same issue? And one in addition had that problem with the dial?

Thanks for clearing that up.