# Canon 100mm 2.8 macro USM lens question...



## Big (Jul 27, 2009)

I just bought a Canon 100mm 2.8 macro USM lens and I noticed that when you focus it manually that when you reach the "limit" it keeps turning even though it's focused to its max. You can keep spinning it around and around. I didn't think this was supposed to do that since my two other lenses stop and you can't turn them any further.
 Is this normal? If not I am on my way back to the area I got it tomorrow and I would really love to know so I can exchange it. It really is a sick lens.
Thanks!!


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## Derrel (Jul 28, 2009)

That is the same behavior that my 100/2.8 USM exhibits. It's normal.


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## Big (Jul 28, 2009)

Derrel said:


> That is the same behavior that my 100/2.8 USM exhibits. It's normal.


Hmmm strange... I thought I broke it haha. Glad i didn't!:mrgreen:


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## musicaleCA (Jul 28, 2009)

So you've picked-up all your new gear? If so, you're in for some fun.


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## Overread (Jul 28, 2009)

Yep its totally normal behavour for USM lenses to have that sort of focus function - its part of the setup that allows you to have full manual focus access even when your auto focus is active - ergo you can use AF to focus and then if you wish use the manual focus to adjust the focus if you wish without having to turn off the AF at any point (though I don't recomend doing this if you are using a continous AF mode like AI servo since then the cameras AF will constantly fight against you and that will wear at the motors - but for single AF mode its great)


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