L Lens Focus Ring

I let someone try my 24L II out and I just felt paranoid about it the whole time when she was rotating the ring.

1. Are there any negative effects of rotating the focus ring of a Canon lens when it is actually set on AF
2. Any difference between L's and non L's?

All L lenses have full time manual focusing...meaning you can manually focus while its in AF, without causing any harm to the motor

Even when the shutter button is not already halfway pressed? Like someone just rotating the ring for fun?

sounds like you shouldn't be lending out your best glass

It won't hurt a thing to turn the focus ring at anytime on your 24L.

Doesn't hurt a bit

Damage? No... it's a feature.

As everyone said, your lens is safe.

For your reference, USM lenses support full-time manual focus (FTM), be it an L lens or not. Those lenses with micro-motors or arc-type motors can theoretically get damaged if the focus ring is rotated while in AF. The reason is the gears that mechanically connect the motor to the AF mechanism.

ctrlcctrlv wrote in post #10809712
Even when the shutter button is not already halfway pressed? Like someone just rotating the ring for fun?

While your lens is fine, there is really no need for anyone to be playing with the focus ring unless they are actually focusing the lens. If you don't correct them, the next time they might do it to a non-USM lens and damage the focusing motor or the gears.

It's your responsibility now, put her in her place

mxracer535 wrote in post #10809695
All L lenses have full time manual focusing...meaning you can manually focus while its in AF, without causing any harm to the motor

EF 85mm f1.2L will not focus in AF mode.

But no, the are designed to allow manual override of focus. Most consumer lenses do it, but it needs to have a Ring type USM(only the 50mm F1.4 can have manual focus in AF mode, and it is not a Ring type USM).

Nick

Well the lens focus ring does have an built life span. And turning it more just for fun will make it wear down faster. But I wouldn't worry about it. It's not like the nifty fifty which will break when you do that.

This is another reason why I ONLY like lenses with either full time manual focus (all USM) or which just spin the focus dial in AF mode (e.g. 50mm f/1.8 Mark I, Tokina 11-16 f/2.8 ), that they can't be damaged by turning the wrong ring. I always hated lending people my Rebel with EF-S non-USM kit lenses because if they confused the zoom and focus rings they could strip the focus gears.

good rule is to never let anyone use your lens, especially the L glass

Koshin wrote in post #10844369
good rule is to never let anyone use your lens, especially the L glass

L lenses should have a build quality sufficient that you can't break them simply by using them. Now, letting your 2 year old walk around with your L lenses is not good but you should be able to hand your camera and L lens to a competent adult to have them use it without fear of breaking it aside from a big accident of some sort.