Focus ring moves while in AF - Problem?

[FidelCastrovich]

Hello all,
I recently purchased a 30D (first digital, woo hoo!) with Sigma 70-200 f2.8 and Canon 17-55 f 2.8.
I've noticed that even when the lenses are set to AF, the focus ring(s) can be moved, and indeed, sometimes i forget and adjust focus manually.

Is it supposed to be this way?
Does it harm the focus motor or any other mechanism in the lens to do this?
Why doesn't it lock when in AF, like on my Minolta lenses?

Thanks a bunch.

 

[lostprophet]

everything is working as it should with those lenses, its known as full time manual focussing

 

[FidelCastrovich]

everything is working as it should with those lenses, its known as full time manual focussing

Yep, that was my hunch alright - that it was intentional and had a cool stage name, such as "Full Time Manual Focusing".

However, i do remember reading somewhere (manual maybe?) that i shouldn't move the focus ring when in AF. Which is what confused me in the first place.
The manual has since been thrown away, however, so i can't check again.
What's that about?


Thanks again.

 

[xfloggingkylex]

if the focus ring moves easily you are fine. Basically the AF motor has a clutch that automatically engages when you move the ring. My kit lens has a system like this, but on my 50mm 1.4 if the camera is set to AF, the focus ring is tight and doesn't freely move (and if you do move it you can hear the motor turning - not good).

 

[lostprophet]

Yep, that was my hunch alright - that it was intentional and had a cool stage name, such as "Full Time Manual Focusing".

However, i do remember reading somewhere (manual maybe?) that i shouldn't move the focus ring when in AF. Which is what confused me in the first place.
The manual has since been thrown away, however, so i can't check again.
What's that about?


Thanks again.

The Canon uses USM or Ultra Sonic Motor and the Sigma uses HSM or Hyper Sonic Motor which are the same but they have to use different names.
Because of the way they are made you can adjust the focus without having to switch the lenses to MF, which can save time. Unlike non USM or HSM lenses you will not damage the motors by turning the focus ring whilst in AF

 

[FidelCastrovich]

Thanks all. Another tiny step to gaining total control over this magnesium beast packed with features - the 30D.