Using a DSLR for Broadcast work
The Canon 7d and 5d mark 2 are HD, so they can be used for HD broadcast work right?
This is the kind of question I have come across and the answer is yes and no. A huge number of cameras are classified as HD as they record 1080p, i.e. they record 1080 horizontal lines of resolution (as opposed to standard definitions 480). However, the footage that they record is compressed in one way or another and this is where certain formats can be rejected by broadcasters.
As far as the BBC is concerned HD DSLRs are not on their list of acceptable HD cameras as it stands now. The reason for this is the compression ratio. Without getting too geeky about this, cameras can compress images by ditching information, giving less resolution for chroma information than for luma (in simpler terms colour and brightness). This is expressed as a ratio, for example:
4:4:4 This would indicate no compression
4:2:2 Essentially some of the chroma info has been ditched here. That said, 4:2:2 is still a very high end HD recoding format (used on cameras such as top end HD XDCAM and HDCAM)
4:2:0 DSLR's compress footage into a format known as H.264, which puts them here.
However, every broadcaster has their own values of what they can accept as being HD, the BBC is probably one of the less forgiving broadcaster for this. Having said that, even in a BBC HD programme you are allowed a certain percentage of non "HD footage". You may not be able to use your 7d or 5d as the main camera, but you can certainly use it.
Will this change?
Almost certainly, it is just a question of when. Canon will announce their 5d mark 3 before long, there are so many rumors floating around about what it will and won't have that it is not worth commenting on. The point is, at some point Canon will release a camera that uses a different codec with less compression, the only question is when.