Bluescreen vs Greenscreen

Pigman II

I was watching some of the StarWars 'making of documentaries' a while back and one thing I took from them was that some of the digital background shots were been achieved using actors against the classic 'blue background' whereas others were done using green.

Now I understand (roughly) what blue and green can offer you but I can't work out why (in the case of SW anyway) why one background colour is chosen over the other. Is it something to do with the colour tones that will eventually appear in the background or is it because some shots need to have steam/smoke etc kept in there? I wonder could someone briefly explain giving examples from movies why green is sometimes used instead of blue?

Thanks!

Kazaanova

I know you're probably joking, but, as far as I can guess;


The way it works, as far as I can tell from using Photoshop is that you film an actor infront of say, a bluescreen. You put that into the computer, and the computer goes through thousands of frames and automatically selects anything with the colour blue in it. It deletes anything with that color in it(the background), and then replaces it with something like a photo background or a CGI motion background.

Human skin has very little blue in it, so shooting humans in front of bluescreen is probably easier than green. But if the actor had say, blue hair, they couldnt use bluescreen because it would get messed up, so then they'd have to use green. If they were shooting someone in front of greenscreen, and that person was wearing say, green makeup, the computer would get confused selecting green and select the makeup too, so they'd have to use bluescreen.

Pigman II

Nah not joking. I could understand and accept if it was as simple as the final shot being in done in blue to retain a green element or done in green to retain a blue element but I don't know if it's as simple as that?

Take for example the duel between Anakin and ObiWan in Ep3. All shots are eventually in darkish environments (most dark red and some darkgreymetalic) yet as far as I remember some were shot against a blue bg and some were shot against green.

Now I admit I haven't gone thru them shot for shot to see what cooresponds to what but I can't off hand spot obvious pattern so I was wondering if there was a simple explaination as to why it is so?

BolBill

The way I see it is that this thread should be in the Film PRODUCTION area, not here