T3i Autofocus Lens

[sidney1996]

If I bought a new lens to replace the original lens that comes with the t3, will it then autofocus?  Or is autofocus not related to the lens, but to the camera? I know t3i doesn't support autofoucs but I was just wondering if it could be fixed with a new lens or not. Thanks so much!

[RobertTheFat]

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@sidney1996 wrote:

If I bought a new lens to replace the original lens that comes with the t3, will it then autofocus?  Or is autofocus not related to the lens, but to the camera? I know t3i doesn't support autofoucs but I was just wondering if it could be fixed with a new lens or not. Thanks so much!

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On any Canon camera with removable lenses, the autofocus motor is contained in the lens. (The camera has to recognize an autofocus lens, of course, but they all do.) So if you buy a Canon-compatible autofocus lens, it should work fine on your t3 or t3i.

There are cameras of other manufacturers (some Nikons, for example) in which the autofocus motor is contained in the camera. But no Canons work that way.

[cicopo]

It would be quite difficult to buy a lens with the EF or EF-S mount that didn't have the ability to AF. Just check that the switch on the lens is set to AF.

[TCampbell]

The overwhelming majority of lenses (Canon lenses or 3rd party lenses designed for compatibility with Canon EOS cameras) include auto-focus and work with the camera to auto-focus (the lens does the focusing, but the camera's sensors tell the lens what to do.)

I can only think of (off-hand) 5 Canon lenses that don't have auto-focus included and they are all highly specializied lenses (e.g. "Tilt Shift" lenses never have auto-focus).  Even among 3rd party lenses, most all of them tend to be auto-focusing lenses and I can only think of a few (highly specialized and rather expensive) which are manual focus.

The only lower-cost lenses I can think of which are NOT auto-focus are "mirror lenses" -- typically these are long telephoto lenses at a somewhat low price point given their focal length.  They are all manually focused (all that I know of) and most of them aren't actually camera brand specific... they often just have generic "T-threads" and you have to get a T-adapter (a ring which has an EOS mount on one side of the ring and t-threads on the other side of the ring).    Not only do those lenses have manual focus, they usually don't even have aperture control (it would be more like putting the camera on the back of a telescope... the camera can't auto-focus the telescope and the telescope doesn't have aperture blades like a camera lens.

[Skirball]

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@TCampbell wrote:

I can only think of (off-hand) 5 Canon lenses that don't have auto-focus included and they are all highly specializied lenses (e.g. "Tilt Shift" lenses never have auto-focus).  Even among 3rd party lenses, most all of them tend to be auto-focusing lenses and I can only think of a few (highly specialized and rather expensive) which are manual focus.

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And the MP-E 65 macro.  Again, a highly specialized lens.

The only non-specialized one I can think of is the Rokinon 14mm ultra-wide.  Which is full manual mostly because it's so **bleep** cheap.

[TCampbell]

I did not know about the Rokinon.  

None of the tilt-**bleep** lenses are auto-focus (from any brand) so that's four from Canon, plus the MP-E 64 speciality macro (I did know about that one).  So that's 5 from Canon that I can think of.  Everything else I can think of from Canon has an auto-focus motor.

I believe all "mirror" lenses (Maksutov-Cassegrain optics or Schmidt-Cassegrain optics using corrector plates and mirrors -- basically catadioptric lenses that are effective just very tiny "telescopes" mounted to the front of the camera) generally never have an auto-focus motor (and also generally don't have any option to change the focal ratio other than to put a "mask" on the front of the lens to stop down the light collection surface area).  You could go to a site like B&H Photo and search for "mirror lens" and find a whole pile of them.  Their advantage is that they're CHEAP considering their focal ratio.  Optically they're not so great and all out-of-focus blur (which always takes on the shape of the aperture) basically defocuses to "donut" shaped circles (because the lens has a center obstruction so the black shadow in the middle is the center obstruction).  This gives the mirror lenses an exceptionally unflattering "bokeh".