Hi, i made some great video with the T2i, with a bokeh lens and manual focussing.
But what if i want to shoot action with a T2i?
For this i need a lens which give me constanly autofocus?
Anyone now some good lenses for this and for decent indoor shooting?
Price is my priority.
thnx

It doesn't exist. You will struggle with any fast action work, using a DSLR. That sort of work really cries out for a dedicated video camcorder,

As you get more use on these cameras, you come to understand why film crews have a dedicated focus puller and use tape measures and "positions" for the actors. When trying to catch fast paced, unplanned action I'm very fortunate to be able to use 50% of the footage. That's why I recently purchased a TM900 video camera. Horses for courses.

ok, thnx for reply, but what i don't understand though, I see multiple skate-movies who do stay in focus while everything is in motion, ...
Skate slo-mo test - Canon 550D - YouTube (http://www.youtube.com/watch?v=Zkjm2mJZ4Do)
Summer Throwaway HD-Tage 2 - YouTube (http://www.youtube.com/watch?v=gy8Ac-MFtHY)
Swandle DSLR Handle | Video - YouTube (http://www.youtube.com/watch?v=wFQkfOADpIE)

They don't use a followfocus i suppose,
which lens can handle so much movement, while being focused?

They are "staying in focus" by shooting with a deep depth of field. That way they just follow the action without having to actually pull focus constantly.

Read this: Hyperfocal Distance (http://www.dofmaster.com/hyperfocal.html), and pick up a DOF calculator for your smartphone. With a wider lens you can attain a very deep depth of field fairly easily.

Yes, if you use a wide angle lens and/or shoot around f11 or higher, you can keep things in focus pretty good. Either will help immensely, both make it possible. You do, however, lose some of that "look" of a shallow depth of field that the DSLR's are known for. Personally, I think the ultra-shallow DOF has about run its course. I like everyone else ran out and bought a f1.4 lens, then found it impossible to use in that range. I seldom shoot below f2.8 now and prefer f4.

Does someone knows some cheap lens-models i could buy to do this...and suitable also for lowlight situations?

For run-and-gun work is you definitely want a stabilized lens. Perhaps the best value for a Canon with an small sensor is the Tamron 17-50 f2.8:

Tamron SP AF 17-50mm f/2.8 XR Di-II VC LD AFB005C700 B&H Photo

It's one of the highest rated lens on SLR gear site:

Tamron Lens: Zooms - Tamron 17-50mm f/2.8 XR Di II VC LD Aspherical IF SP AF (Tested) - SLRgear.com! (http://www.slrgear.com/reviews/showproduct.php/product/1297/cat/23)

My only complaint is the focus ring is a little gritty, unlike much more expensive L glass. I've heard good things about some of the Sigmas, but haven't personally used them.

Does someone knows some cheap lens-models i could buy to do this...and suitable also for lowlight situations?

If you want cheap, then you are really talking vintage primes with an adapter. In many cases you will exceed the IQ possible with a modern zoom.

I would recommend picking up an m42 28mm f/2.8 vintage lense, which will cost you next to nothing. Here is an example:

M42 Helios 28mm/1:2.8 wide angle lens. A bargain!! | eBay (http://www.ebay.co.uk/itm/M42-Helios-28mm-1-2-8-wide-angle-lens-bargain-/230665029575?pt=UK_Lenses_Filters_Lenses&hash=item35b4b507c7)

This type of lens will give you the deep DOF talked about here at narrow apertures, but offers good low light capability too. You will need to search this forum to get the info on adapters.

For fast pace action, It's best to use a widest lens you can while still getting the look and framing you want. DPW August Anarchy 2011 DVD Preview - YouTube (http://www.youtube.com/watch?v=yWlgK2-VvBI&feature=channel_video_title) - I shot that using my kit lens mostly at the 18mm range so that I knew it'd be easier to focus quickly and wouldn't be too wide that it looked strange. One thing I would have liked to test was shooting at a higher shutter, as I shot that using the 180 degree rule, so at 1/50 as I was shooting at 25p but it might have been better to shoot at 1/200 but I would have lost a lot of light and I was already shooting at quite a high iso if I remember correctly.

thanx matt for your example, the kit lens isn't sufficient for me by the way, coz i shoot a lot in lowlight where it fails to do a proper job.

For run-and-gun work is you definitely want a stabilized lens. Perhaps the best value for a Canon with an small sensor is the Tamron 17-50 f2.8:

Tamron SP AF 17-50mm f/2.8 XR Di-II VC LD AFB005C700 B&H Photo (http://www.bhphotovideo.com/c/product/652136-USA/Tamron_AFB005C700_SP_AF_17_50mm_f_2_8.html)

It's one of the highest rated lens on SLR gear site:

Tamron Lens: Zooms - Tamron 17-50mm f/2.8 XR Di II VC LD Aspherical IF SP AF (Tested) - SLRgear.com! (http://www.slrgear.com/reviews/showproduct.php/product/1297/cat/23)

My only complaint is the focus ring is a little gritty, unlike much more expensive L glass. I've heard good things about some of the Sigmas, but haven't personally used them.When I bought my 600D(T3i) I went cheap & bought that Tamron 17-50 f2.8 VC. It was horrible compared to a good Canon lens. The AF was slow, the IS very noisy, to use it in MF you need to slide the switch otherwise you are fighting the focus gears. Finally the zoom & focus rings turn the 'wrong' way compared to all my Canon lenses.

I returned the Tamron lens the next day & upgraded to a Canon EF-S 17-55mm F/2.8 IS which is wonderful lens & would surely have an 'L' designation if it were a full frame rather than EF-S lens. It cost more than the camera & over 2X the price of the Tamron but it was worth it.

This is the problem with lenses, they cost alot...is it worth to invest in this...damn...maybe a good way to start as a side-project in photography.