Green/Blue Screens

[MacNoobie]

I'm working on a hobby project, kind of a parody of all the Arby's commercials going around lately and my question is with a green/blue screen is there anything special about the screens that I have to know about, i.e does it have to be a certain shade of blue or green or can any blue or green work, also is there any way of making your own maybe buying a huge piece of posterboard or foam board, buying some green/blue spray paint and painting it over and putting it behind the person?

 

[Mr. Anderson]

you want to make sure the lighting on the screen is as uniform as possible - no shadows. It can be a bit tricky.

What are you going to use to edit the video with?

D

 

[MacNoobie]

I was planning on buying flat florescent paint or some fabric and seeing if I can do it that way since no one in town (and I mean no one) sells anything officially for blue/green screening. I'm going to use FCP 5 to edit the DV material and probably H.264 for the video.

I dont know if anyones ever tried to spray paint a flat foam board or have some inexpensive cloth to do a key off of but I'd love it if someone whos done the spray paint method could mention maybe any brand or types of paints that work the best for it?

I'm planning on doing it outside also since I dont have the best lighting in my home. Any tips on when to do it maybe which way the matte and actor should be facing?

 

[JeDiBoYTJ]

technically if your colors on the camera are good, and your screen is lit well, you can use any color, because with FCP you can key out any color. although green and blue are the most popular because they are easiest colors to see and they dont 'bleed' around your character.

but remember to light your screen well! shadows will easily throw it off (believe me, its a pain in the rectum when you have shadows).

 

[ke5awf]

Not Any Color

Yes, technanilly you can use any color, But you must remeber that when you take a color out in FCP it will take that color out of everything in the image. the best way to do it that i have seen, and used, is to take a lime green screen and have a backlight on the image, so as to sepearte it from the background color. then go into FCP and take out green in the filter, and that will give you a better quality image, with as little as possible color taken out of the main image.

 

[LethalWolfe]

Yes, technanilly you can use any color, But you must remeber that when you take a color out in FCP it will take that color out of everything in the image.

Correct. And it shouldn't come as a surprise that the three best chroma key options are also the three primary colors of light (red, blue, and green). If you want you can use a purple as you key color, but then you're asking the computer to key out a mix of red and blue. That will be harder than using a "pure" primary color.

Red isn't used very often because skin tone has red in it, and green, IIRC, is used most often because there is more image information in the green channel than in red or blue.


Lethal

EDIT: Something to always remember is that the software sees colors, not shapes. So if you tell it to key out everything that's green so good bye to your green screen (good) and your actor's green eyes (bad). Obviously you can tweak the settings to help isolate the exact color you want to key out, but I have seen people w/very blue eyes cause problems when they've been shot on a blue screen.

 

[obeygiant]

one thing no one tells you about blue/green keying unless they have done it is about the lighting ratio. The green screen HAS to be at least one F-stop below the object (one stop darker) or else you will get a green halo around the object. So dont flood the green/blue screen with TONS of light. Just make sure the object is far enough away from the back ground and lit brighter than the background to prevent the color bleed that will screw up your matte.
anything not intersecting movement can be "garbage" matted.