who has full frame video as in I mean full pixel count its all down sampled. Full red I guess would rock...
FF video means that when you stick a 24/1.4 lens on your camera, you get a horizontal AOV of 73.74° and a DOF of f/1.4 at 24mm. That will affect the perspective. If you want practical numbers, if your subject is 2 meters away, your horizontal coverage (how much you see to the sides of your subject) is 3 meters. If you put the same lens on a RED camera, you get a horizontal AOV of 53.89°. This means that you'll only capture 2.03m of the environment horizontally if your subject is 2 meters away. This will look different. The chair on the left of the subject and the hanging tree branch to the right of your subject that were visible in the frame when you used the lens on FF are not visible on your RED camera. The DOF will also be different (deeper) on RED. Also, it's not "down sampled", it's line skipped. The full sensor is used, but only 1080 vertical lines are read out of all the vertical lines to get 1080 resolution video, likewise for horizontal (1920).
so 5d 3 is a 4k camera?
Not with factory settings...
You can come pretty close to 4K with Magic Lantern.
Canon 7D2 X 2 - EF 16-35mm f/2.8 L, EF 85mm f/1.8, EF 100mm L f/2.8 Macro, Custom Cine 50mm & Custom Cine 35mm.