Filmmaking / Directing : Roland Emmerich Breaks Down Sci-Fi Scenes from His Career | Vanity Fair by Brian Onley

This is a great post!

Thanks Kristin!

I would really like to hear from a DP / Cinematographer concerning the move from green screen to blue. Originally, the green that was chosen happened because it was a color green that you would never use in sets or costumes. There is a problem with green screen and outdoor shots where you can lose some of the grass/trees, etc. But I question the choice of blue because you will lose some sky shots due to the blue conflicts.

Is there a protocol for the choice? Thanks again :)

In terms of chroma keys, I believe blue was the first choice used, in Thief of Bagdad. The general change to green came later. Green because it was farther from any colours in skin tones than other colours its easier to key out. remember this was a purely photographic process. With more and more computer power now available, backdrop colours can be very accurately defined and removed really well. The narrower the frequency of the light source, essentially the purer the specific colour, the better

I have shot yellow keys using very narrow spectrum sodium vapor lights, and red screen as well to name a couple. Choices had mainly to do with colours in the foreground elements, but other considerations like available power came into play. Red screen was for a product commercial and I had to rotate my crew off of the set as peoples temperaments were being affected by the intense colour environment. Yep, something to that colour theory stuff.

Any colour can be used to key, just depends on time and money in VFX. Black and white can also be used to key with a luminance key.

The colours being keyed, just disappear scene with the foreground material you wish to keep. The colour of the key does not effect colours in the background plates that replace the colour screens in the final picture.. Thus on a green screen shot we can see an actor and a flatly lit green behind them. When the green is removed, the image, minus the green, can be laid over another image without affecting the colour of that background plate. The shot of the background plate is not having any colour keyed out. So a background of grass and trees can have a foreground layer that was green screen, with the green removed, without any effect upon the greens in the background. Same with the blue sky and blue screen, they are separate shots with only one of the shots having a chroma key applied.

The colours we use, Chroma Key Green, Ultimatte Green, Digital Green, and their blue counterparts, are all quite different from most colours we see in the real world. With the ability of current keying software, this process is now quite simple. Of course there are things that can cause problems. Reflective surfaces for example. Light hair colours and backlight, particularly LEDs, can cause colour fringes that play havoc with keys.