Is it OK to focus manually on Canon EF lenses with AutoFocus ON? ?

Question

I have two Canon EF lenses: 18-55mm IS and 55-250mm IS. Does it in any way damage the little AF motor if the AF is on and I still turn the manual focus ring? I hear a small mechanical noise when I do so, and I don't hear it when the AF is off and I turn the ring.

Answer 1

No it is not OK as you could damage the autofocus motors that way since those lenses don't have Full Time Manual Focus. You really should turn the autofocus off on those your lenses if you want to manually focus. You will find Full Time Manual focus on [most] Canon lenses with an Ultrasonic motor. I put most in brackets because not all Ultrasonic lenses have Full Time Manual focus... you just have to check Canon's website or the manual to see if it does.



You probably haven't damaged your lenses yet, so nothing to worry about. If I were you, I'd make sure I turn the switch to MF in the future when you want to manually focus.

Answer 2

Here's my simple answer.



Those are not L lenses

Nor is it a USM AF lens.



You can only do this if the lens is one of Canon's extremely expensive L lenses, or one that has a proper focusing ring, which also comes with a USM focusing Motor. Since those lenses surely aren't L's, and don't have proper rings, you really shouldn't do that, you will damage the lens.



Canon should have done what Nikon did: stop the user from turning it all together when it's in Autofocus, with the kit lenses. Also, what sense does it make to do what you do? You're trying to focus manually, and then when hit the Button, it will focus on something else. Just put it on M focus, why risk the lens for fun?

Answer 3

The answer depends on the lens. If the lens has a USM ring motor, it's ok to MF while in AF mode. If it's any other form of AF motor you must switch to MF mode to MF. Your 18-55mm does not have USM ring so you will need it to be in MF mode. The 55-250mm also does not seem to have a USM motor.



So in short, with your lenses you must be in MF mode to MF. If you happen to ever buy any USM ring lenses you will be able to MF in AF mode.