I am playing with my new 550d. I cannot see a way to shoot video with shutter or aperture priority as in still mode (and as in the high-end consumer camcorders). I mean in a way when choosing a shutter speed or diafragm, the camera adapts diafragm or shutter speed automatically according to light conditions. Do I miss something?

Turn the AE setting to manual, that should allow you to adjust each individually in video mode.

"M" for manual. All other modes are automatic.

The new firmware for the 5D2 will add Ta and Tv modes. Maybe that feature will come to the other DvSLRs before long...

"M" for manual. All other modes are automatic

Not on the 550D. "M" is for photo only. 550D has a dedicated video mode (at the other end of the dial).

Pages 127-128 of the English manual explains in detail how to setup for manual exposure in video mode.

Just leave the dial in movie mode and adjust aperture, shutter and ISO settings as you would normally do in the 'M' mode. It's that simple :-)

I know exactly what you mean and the answer is no.

Because the video mode is selected by the dial ring.

Everything is full auto, or full manual (except ISO which can still be auto in manual mode)

I'd say, choose your iris, shutter speed and let ISO do the exposure automation.

But you wont know if you're using ISO 3200 which is not suitable for every situation or quality requirements.

I used the 7D before and I dont remember if the AV or TV dial is really AV or TV when you choose movie mode.

I think it is like the T2i/550d and fully manual when in movie mode.

The reason is that you dont want your iris or shutter speed to change when shooting. It makes your footage unusable.

You'll have to get used to control both iris and shutter speed at the same time.

good luck!

But you wont know if you're using ISO 3200 which is not suitable for every situation or quality requirements.
It's too bad that the T2i doesn't use it's new feature for Canon 'Setting the Maximum ISO Speed for Auto ISO' (pg 63 of the manual) for video as well. Maybe in a future firmware update or Magic Latern.

Most videographers and filmmakers recommend keeping the shutter speed at 1/50th for 24p and 1/60th for 30p. It seems that aperture and ISO are the only variables you'd want to change in Manual, except in certain circumstances.