5DIII AF started hunting?

[luckydude]

I've got a 5DIII firmware 1.2.1 that I took to Europe with me. 2nd day in I noticed when I use all the AF points with a 24-105 mark I
it is hunting, to the point that AF is basically useless. This was in bright light at the beach in Holland, so light should not be an issue.

Here's the weird thing, when I put the camera in full auto mode it works just fine, it seems to hunt in M/Tv/Av. This is in one-shot mode, not AI-servo.

Maybe it's just the nature of the beast, it hunts more at wide angle because it has more to lock onto, but I'm not used to it running the focus ring back and forth forever, that's never happened before. Hard to believe I've never used all the focus points with a 24mm lens.
It's possible because I mostly shoot sports on the center point or the center cross.

Is this normal? Or did one of the kids drop the camera?

I just tried with the 16-35 III - same thing, it hunts like crazy when using all the points. Works fine with a 3x3 in the center. Move it over to the far right or up from and it hunts like crazy. Any ideas? Something is clearly not right with some of the AF points.

Other info: pulled the lens, put it into movie mode and started it, looked at the sensor, it's perfectly clean, mirror is clean, the glass at the top of the camera looks aligned and clean. So what can make some of the AF points die? Is this fixable or time for a 5DIV?

Wishing I had taken the 1DX instead, it's heavy but the focus works :'(

 

[Ian_of_glos]

I've got a 5DIII firmware 1.2.1 that I took to Europe with me. 2nd day in I noticed when I use all the AF points with a 24-105 mark I
it is hunting, to the point that AF is basically useless. This was in bright light at the beach in Holland, so light should not be an issue.

Here's the weird thing, when I put the camera in full auto mode it works just fine, it seems to hunt in M/Tv/Av. This is in one-shot mode, not AI-servo.

Maybe it's just the nature of the beast, it hunts more at wide angle because it has more to lock onto, but I'm not used to it running the focus ring back and forth forever, that's never happened before. Hard to believe I've never used all the focus points with a 24mm lens.
It's possible because I mostly shoot sports on the center point or the center cross.

Is this normal? Or did one of the kids drop the camera?

I just tried with the 16-35 III - same thing, it hunts like crazy when using all the points. Works fine with a 3x3 in the center. Move it over to the far right or up from and it hunts like crazy. Any ideas? Something is clearly not right with some of the AF points.

Other info: pulled the lens, put it into movie mode and started it, looked at the sensor, it's perfectly clean, mirror is clean, the glass at the top of the camera looks aligned and clean. So what can make some of the AF points die? Is this fixable or time for a 5DIV?

Wishing I had taken the 1DX instead, it's heavy but the focus works :'(

What is "Lens Drive When AF impossible" set to - You can find it on AF Menu 4
With my 5D mk3 I have found that if this is set to "Stop Focus Search" the AF gives up very quickly and I cannot achieve focus. That might be what is happening here.
There is no reason why AF should misbehave with the 24-105 or the 16-35 iii. I use both these lenses and I have never had an AF problem with either of them.

 

[luckydude]

What is "Lens Drive When AF impossible" set to - You can find it on AF Menu 4
With my 5D mk3 I have found that if this is set to "Stop Focus Search" the AF gives up very quickly and I cannot achieve focus. That might be what is happening here.
There is no reason why AF should misbehave with the 24-105 or the 16-35 iii. I use both these lenses and I have never had an AF problem with either of them.

It's set to "On". I haven't had problems with these lenses either until now.

 

[hne]

Dirt on the AF chip? Hard to see down there, but mirror up, rocket blower at the bottom of the well. Has saved me before when some AF points all of a sudden started to act up.

 

[Mt Spokane Photography]

Dirt on the AF chip? Hard to see down there, but mirror up, rocket blower at the bottom of the well. Has saved me before when some AF points all of a sudden started to act up.

I've seen a number of similar posts where cleaning the AF chip solved the issue. It can get dust or a dirt particle on it, its not common, but happens enough that I've seen a few posts over the years.

 

[luckydude]

Dirt on the AF chip? Hard to see down there, but mirror up, rocket blower at the bottom of the well. Has saved me before when some AF points all of a sudden started to act up.

Sounds like a possibility but at the bottom of what? The glass at the top of the opening? I don't get "bottom of the well",
forgive my ignorance.

 

[hne]

Dirt on the AF chip? Hard to see down there, but mirror up, rocket blower at the bottom of the well. Has saved me before when some AF points all of a sudden started to act up.

Sounds like a possibility but at the bottom of what? The glass at the top of the opening? I don't get "bottom of the well",
forgive my ignorance.

Put your camera in manual sensor cleaning mode. Between the lens contacts and the sensor there'll be a bunch of holes. Hold your camera upside down so dust can fall out and use a rubber blower with dust filter to blow clean air down (now up) those holes.

There's a picture here:
https://www.dpreview.com/forums/post/31210296

 

[Mt Spokane Photography]

Dirt on the AF chip? Hard to see down there, but mirror up, rocket blower at the bottom of the well. Has saved me before when some AF points all of a sudden started to act up.

Sounds like a possibility but at the bottom of what? The glass at the top of the opening? I don't get "bottom of the well",
forgive my ignorance.

https://learn.usa.canon.com/resources/articles/2017/how-does-af-work.shtml?categoryId=123


Below is a schematic showing the AF sensor (#11). It sits down under the mirror.


http://www.sensorcleaning.com/whatisanslr.php

 

[Buck]

I am finding similar results with mine as well, does not happen all of the time but happens more frequently than I would like. I find my self slowly panning to get the AF to lock on to the subject. I am finding that it happens much more often when shooting in vertical. Just had the sensor cleaned, don't know if they cleaned the AF chip.

 

[Ozarker]

Is this fixable or time for a 5DIV?

It isn't fixable. Like you said, "...time for a 5D IV."

I'll give you $100 for it so that I have spare parts. Go get the new camera. I wouldn't bother the Canon service guys with this.