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?

[ebiggs1]

Menu>Tools tab>Clear all settings and also Clear all custom settings.

Do the test!

"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."

[ivanti]

Thanks! I will try that. I wasn't set to AI Servo, but when the issues started, I tried it.  I had forgotten when to use it so I wanted to rule it out. For as bright as it appeared to be in that room, I really was having to crank up the ISO and I was getting too much grain.

[ebiggs1]

Most people don't understand how Ai-servo or most of the other focus assisted modes work. 98% of the time One Shot will be the best focus mode to use. Ai-servo does not confirm focus achieved and will fire the shutter no matter what.

[ivanti]

Do you know if AI shows in the metadata? I'm wondering what my setting was when the focus problem occurred?

[FloridaDrafter]

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@ivanti wrote:

Do you know if AI shows in the metadata? I'm wondering what my setting was when the focus problem occurred?

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Yes. I opened two of the images you posted in DPP 4 (first and third) and the first one you used "AI servo", the third is "AI focus AF". I could also see the focus points the camera used.

Newton