Stealing this from /p/:
The t3i is a solid, cheap starter body for video-- does 1080p in 24p, has some basic audio management controls, a good range of lenses available. You can get it with a kit for sub $600. Though, to be honest, I'd say there are two better routes you could go for video:
If you're willing to deal with used equipment (and in the case of the GH2,spend a teensy bit more overall), I'd recommend checking out B&H or ebay for a Used Panasonic GH1 or GH2. Both have very high IQ out of the box for video, with full compatibility of every m4/3 lens out there. The nice thing about MFT is that you can also adapt upwards to any lens without any worry of vignetting because its a smaller sensor size than APS-C or full frame. The GH1/2 also let you use the viewfinder during video mode, which canon doesn't permit. On top of that, both can be easily hacked once you get the hang of them to really, really boost the image quality, some professional-quality films have been shot on a hacked GH2 (albeit with some really nice glass), most notably Shane Carruth's "upstream color" last year.
The other recommendation, though, if you want to go the canon route-- and i'm sure i'm gonna get some heat from others in here, is the unfairly maligned Canon EOS M. Hear me out-- you cannot get a higher-image-quality video camera for $300 new, period The EOS M is basically a T4i in a box the size of a point and shoot, with no viewfinder or articulated LCD, a touchscreen-heavy interface, and shoddy AF out of the box. Also, its proprietary lens system,EF-M, only has two lenses, and the canon brand adapter is overpriced. Sounds like a nightmare, right?
Well, here's the thing: Canon fixed the auto-focus in a firmware update-- now its about on par with the AF in the rebel line (AKA: acceptable to solid), and while I'm not a fan of AF servo in general, this is one of the better incarnations of it because you can simply tap on the screen and focus. Moreover, you should use more MF than AF in video anyways. ON the touchscreen subject, the touchscreen works incredibly well-- its a smartphone quality interface, but more importantly, you can do everything with the physical buttons and radial dial with ease enough for me at least.
On the subject of lenses: the two proprietary ones are both great--- the 18-55 kit is noticeably sharper than the standard EF-S 18-55, and the 22mm f/2 pancake is one of my favorite lenses-- beautiful in low light, and most importantly, this camera is so small that with the 22mm, it can fit in a pocket.
On top of that, while the canon-brand standard EF (the standard canon lens mount) to EOS M adapter is an absurd $125, fotodiox has one that preserves both autofocus and image stabilization for a mere $60-- as someone who tried out both, the fotodiox works perfectly, and that's the one i kept.
So, on it's own, this is a camera that does high quality 1080 24p video, has a very small form factor for discreet filming, two great, cheap, and small proprietary lenses, easy compatibility with every other canon lens, and magically-revived autofocus that is more than adequate. For $300 with a lens.
This on its own would be a great deal, but when you factor in the custom Magic Lantern firmware, the EOS M becomes the biggest steal imaginable for a beginner making video. ML is a sd-card mounted hack firmware that adds features like focus peaking (highlights what parts of the image are in focus or out of focus in manual) to video, and even allows for the recording of RAW video-- albiet in 720p. It gets better dynamic contrast out of the M as well.
So there you have it-- it's a small, discreet camera that can fit in your pocket in some permutations, and can also have a gigantic telephoto lens shoved on it in others. It records video as well as any other camera in the Rebel DSLR line, and it costs $300. Canon is really trying to shovel off remaining stock of it through 3rd party retailers at this point so it's worth pulling the trigger on to try-- you could always return it. But tbh, an EOS M with updated firmware (And again-- the difference between the AF out of the box and the AF after updating is night and day) is an incredible option for a beginner filmmaker.
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