How does one get everything to be in focus while filming with the t2i?

Everything? Stop the lens aperture down to f/16 or so. Also, don't put anything too close to the lens in the foreground.

at f16, would that allow enough light in while filming in broad daylight? I'd be shooting at 720p 60fps (I'm going to be filming people skateboarding), 1/125 shutter speed, and I don't want to push the ISO past 400

It's a 3-way balance to get what you are looking for. As above...F16 works great but you may have to tweak your shutter and iso to get the exposure right.

And then the question, if you want everything in focus, why not use a video camera? Seems like you're taking away the one big strength of the DSLR...DOF.

Although when I fly my T2i on the Blackbird, I'll admit it makes sense to widen the DOF so I don't have to be so precise with the distance I need to be from the subject.

Also, the wider the lens, the more will be in focus. (Okay, technically things are just as out of focus, but they aren't so magnified with a wide lens. But that's a technicality...)

So, yeah, a small aperture (high f-stop), wide lens, and nothing close to the lens will do the trick.

In broad daylight, f/16 (or close to f/16) should be possible.

You mentioned not wanting to push the ISO past 400. I found the noise to be acceptable all the way up to 1600 on the T2i. If I had to choose between focus and a little noise, I would put up with a little noise. Even if you were being really picky, ISO 800 should be OK.

As I understand it, one way to get most everything in you composition in focus would be to get an application like pCam, determine the hyperfocal distance for your lens and settings, and focus accordingly, which should result in everything from your subject back to infinite to be in focus.

Kevin

This site is good for calculating DOF and hyperfocal distances:

Online Depth of Field Calculator (http://www.dofmaster.com/dofjs.html)

So for instance a 28mm lens at f/16 gives you a hyperfocal distance of 8.5 feet. So if you focus at that distance everything from ~4.5' to infinity will be in focus. You could probably go as low as f/8, hyperfocal at ~17 feet which gives you 8.5' to infinity, but it depends on how close you need to be to your subject.

You mentioned not wanting to push the ISO past 400. I found the noise to be acceptable all the way up to 1600 on the T2i. If I had to choose between focus and a little noise, I would put up with a little noise. Even if you were being really picky, ISO 800 should be OK.

Worth remembering noise is not the only trade off against ISO. You also lose dynamic range and S/N ratio at higher ISOs. Not to be ignored when shooting in bright daylight, as often this is where you need dynamic range the most to preserve as much detail as possible.

Consider Neat Video noise reduction if you need to shoot at higher ISOs than you would otherwise like.

i would say you bought the wrong cam for what you are doing. Skateboarding are alwasy moving so you have to have your hand on the focus all the time to follow your subject. I unless you really fast it really hard to keep it up with the skateboarder. Yes DOF look like you are not looking for DOF but rather a better infocus image. Get a Vixia HF S200 or something that way the camcord will do all the work for you.

Well, I didn't purchase the t2i only to film skateboarding. I got it for it's photography aspects (upgraded from an XSi, actually), and I'm not filming just strictly skateboarding, so DOF is still a plus.

And thanks everyone for your answers.

Canon 10-22mm, keep close to your subject.

at f16, would that allow enough light in while filming in broad daylight? I'd be shooting at 720p 60fps (I'm going to be filming people skateboarding), 1/125 shutter speed, and I don't want to push the ISO past 400

As Kodak used to print on the film boxes -

Full Daylight exposure -
Set shutter speed to match film speed (ISO)
Set iris to f16

On the T2i that would be -
Set ISO to 100
Set shutter to 1/100th
Set lens to f16

Should get you close on exposure with deep DOF. Take a still and check the histogram to be sure.
Any clouds or overcast will need more exposure - faster ISO, slower shutter or wider iris.

You mentioned not wanting to push the ISO past 400. I found the noise to be acceptable all the way up to 1600 on the T2i. If I had to choose between focus and a little noise, I would put up with a little noise. Even if you were being really picky, ISO 800 should be OK.

I find that the noise on video is pretty bad compared to noise on still pictures. Even ISO400 is a bit noisier than I would like when shooting video.

Richard

Richard - Thanks for clearing that up. I have been using my T2i for stills mostly and have not used it much for video yet. I didn't realize the ISO affected the picture more in video than stills.
I will be using it for a wedding video this weekend I will have to keep that in mind.