which is better?

what are the advantages and disadvantages of both

and which are better for certain situations?

thanks!

Yo. I _think_ they switched to green screne because the blue naturally accured too often in nature... hmm... that sounds redundant... but yeah.

- C. Davis
President, Alabama Film Club
Owner, Yellow Hammer Films

It just depends on what you are putting in front of it. You cant shoot anything blue against a bluescreen and same goes for green on a green screen. So if your character must be wearing a green shirt then you shoot on a blue screen and vice versa.

Hope that helps,

Cameron

There have been a number of very lengthy discussions about this going around the net lately.

The verdict is pretty much the same...
It depends entirely on what you're planning to put in front if it.
You're going after the most contrast as possible between forground subject an the screen.

In this discussion in the "VFX Pros" forum at Creative Cow, Joaquin (Kino) Gil (FX for contact, Godzilla, Starship Troopers and more), states that:
"Blue was originally chosen for radial (vector) color distance from the skin tones. Green was chosen because it is a good compromise between skin, blue eyes and work clothes, notably jeans."

As more and more people adopt the use of DV for as a way to save costs on their initial projects, a myth that green is better for DV began to circulate. The myth comes seems to stem from two factors:
1) DV compresses color such that for every 4 pixels, color is stored only once, while luma is stored for each pixels. Green, being the brightest of Red/Green/Blue, benefits the most in resolution.
2) Single CCD DV cameras (knowing color is to be compressed anyway) usually have more green pixels than the other colors.

While the facts above are true, they actually don't change the rule about selecting a screen color based on subject colors. You compositing key is going to be defined by CONTRAST between the foreground and background. Even if a green screen has a theoretically higher DV resolution, the edge of your key is dependent on the colors (that CAN'T be green) of the subject in front of the screen, too!

So, what to select ???
Since DV does in fact store luma at four times the resolution as color, light colored subjects (blond hair, pale skin etc.) are best keyed using a darker BLUE screen. Dark objects (black hair, etc.) will be keyed better using a bright GREEN screen.

Bibliography:
"VFX Pros" forum at Creative Cow
FanFilms Forum
DigitalVideoFuel

Hope this helps.
Have fun.

As far as i'm aware, they only moved to green screens for film because the film emulsions have an easier time picking up green than any other colour.

I could be wrong though.

Richard Purves
Living Film
http://www.livingfilm.co.uk/

I've always been told that green captures and reflects more light then blue. That may be why the cameras pick it up better.

Film Director is not a name,
It's a lifestyle.

Some additional points by Steve Wright:

- any subtle video signal advantage arising from green vs blue is totally overwhelmed in the real world by how well the backing screen is lit. Period.

- the main criteria for a well lit green/bluescreen is color separation (very saturated color), proper brightness level, and evenness of lighting.

Steve's visual effects credits include:
Time Machine, The (2002) (digital compositor: Cinesite)
Mothman Prophecies, The (2002) (digital compositor: Cinesite)
Amy's Orgasm (2001) (digital compositor: Cinesite)
Traffic (2000) (digital compositor: Cinesite) (as Steven Wright)
Air Force One (1997) (digital compositor: Cinesite)

He is also the author of the Focal Press book "Digital Compositing for Film & Video".

More of his comments in this posting he made on the CreativeCOW site.

Have fun.

neither is better than the other - both are still used frequently. It just depends on what you want to shoot in front of it.