Turning the focus ring while on AF

[triballistic]

This thing's been bugging me for quite some time.

What happens when you manually turn the focus ring while your camera's in AF? Does it damage anything? How do you know if it did get damaged?

There's a bit of resistance when you do turn the ring so I'm guessing it's a bad thing?

[NeilJohn]

Depends on the lens you are using. There are lenses that are FTM (full time manual) where you can adjust the focus ring anytime, even when in autofocus, to get your desired focus points especially when the DOF is very shallow.

[CruciaL]

This thing's been bugging me for quite some time.

What happens when you manually turn the focus ring while your camera's in AF? Does it damage anything? How do you know if it did get damaged?

There's a bit of resistance when you do turn the ring so I'm guessing it's a bad thing?

There are different AF/MF mechanisms on lenses,

For Nikon's AF-S and Canon's EF L lenses, you can grab the focus ring anytime. It doesn't automatically move so there's no resistance.

On the other lenses like AF-D or sigma or tamron, you should not force the focus ring if it's set in AF mode. Nor should hold it.

[Dekra]

For Nikon, if your lens only has 'A-M' switch on it, then you cannot do manual override during AF as the mechanism locks the focus ring (these are mostly found on kit lenses).

Those lenses with 'A/M - M' switch on it can have you grabbing the focus ring and make adjustments during AF.