EOS 6D Out of Focus

[ivanti]

Canon 6D Mark I with Canon 100-400 EF IS lens

Shooting available fluorescent light at an all day, multi-day event when suddenly on day 2 or 3(?) started losing focus. First, slightly out of focus then completely out of focus. All subjects were at least 20-30 feet away. A couple of times, the shutter would not release. Over 2k photos had reasonably sharp focus. I did get samples (attached).  I suspect a lens issue, but am not sure. Is there a setting that would cause this? Several times, I noticed changes to settings when pulling out of camera bag. Can autofocus lenses be fixed?

[Tintype_18]

Does the camera have different settings for lighting as fluorescent, etc. That would be my first guess.

[ivanti]

Yes, however, the lighting was constant. My camera wasn't.

[Peter]

Is it hair on the two first pictures? Something in the way for the AF sensor?

[ivanti]

Good catch. Hair is likely at a dog show. I didn't notice it when shooting.

[shadowsports]

Greetings,

Start with a simple inspection.  Flashlight and airpuffer (puffer, not canned air).  Remove the lens and inspect the mirror box with a flashlight.  Remove any debris (airpuffer).  Now check the lens (rear).  Same drill (airpuffer) and light.

Remount the lens.  Put Camera into M, Tv, Av, etc.  Perform a full reset of main and custom (C) settings.  Check the buttons on the lens.  Ensure AF, turn off IS if on a tripod.   Retest.

Your images depict a complete AF failure.  If there is not a mechanical failure with the lens, its a setting or switch.   

[ivanti]

Thanks, Rick. I will try this.

[ebiggs1]

First, "Can autofocus lenses be fixed?"

Yes they can but if you have the first version of the100-400mm zoom Canon probably can't service it. So you will need a private shop to do service which may be quite expensive. I doubt it is a hair on the AF mech. It would take a lot of hair to prevent it from working. However it never hurts to clean'er out once in a while.

What I would do is reset the 6D to factory and try again. You might want to do it on a bright sunny day outside. Set P mode. One shot and preferably just the center focus point. BTW for this test never use Ai-servo and a good idea to never use it at all (Ai-servo could have been the problem all along).  ISO 200, WB daylight. Shoot several subjects, not just dogs, from varying distances and make sure there are vertical lines in some. If it doesn't work doing this test it needs service.

[ebiggs1]

Keep in mind......................🤔

A full reset to factory is a critical step and mandatory.

[ivanti]

Thanks. I did a reset. hopefully, I did a full reset, but I'm not sure. Since the problem wasn't consistent, it's going to take me longer to determine if that was the solution,