Why I have to dial in AF micro adjustment now when previously I didn't need to?

Hi,

When I first bought my 6D + 16-35mm II five months ago, my AF micro-adjustment was Zero and spot on!

Today, I noticed that the lens back-focusing and have to dial in + 7 for both wide and telephoto ends. The result is spot on again with + 7. Every shots are now CONSISTENTLY spot on with +7, just like before.

What could have caused the change? Due to work commitment, my 6D and 16-35 have been sitting in dry cabinet mostly. There was no drop or knock. I did a firmware upgrade to 1.1.3 before which has nothing to do with AF. This is quite worrying.

learncanon wrote in post #15868860
Hi,

When I first bought my 6D + 16-35mm II five months ago, my AF micro-adjustment was Zero and spot on!

Today, I noticed that the lens back-focusing and have to dial in + 7 for both wide and telephoto ends. The result is spot on again with + 7. Every shots are now CONSISTENTLY spot on with +7, just like before.

What could have caused the change? Due to work commitment, my 6D and 16-35 have been sitting in dry cabinet mostly. There was no drop or knock. I did a firmware upgrade to 1.1.3 before which has nothing to do with AF. This is quite worrying.

So you did your FW upgrade before the FIRST AF micro-adjustment test? Or just before the +7 dial was needed?

I'm asking that because apparently some people had to change MA after FW upgrades on previous Canon bodies. It would be funny if there was some micro-adjustment variations without external causes!

Was the lighting the same in both test cases? The type and quality of light will give different focus adjustments if they vary between tests.

bsmotril wrote in post #15869424
Was the lighting the same in both test cases? The type and quality of light will give different focus adjustments if they vary between tests.

My experience as well (5D3).

learncanon wrote in post #15868860
I did a firmware upgrade to 1.1.3 before which has nothing to do with AF.

That's what people think.

I recently noticed a lens, which I hadn't used in a while, going completely nuts on my 7D. I knew there was nothing different about it and so I ruled out the likelihood of the lens being bad. I also knew the 7D was fine mechanically.

The problem was still with the 7D: I hadn't finalized the firmware upgrade by removing both batteries (the main battery, as well as the lithium coin battery in the tray). After a few minutes with the battery out, I reconnected everything, resychronized the time with EOS Utility, and I was back in business with better AF capability than before.

Before you try anything else, pull the batteries (both of them) out for a few minutes.