Green Screen?

[vi0lentjuggal0]

i want to make a music video where it has somebody singing but i want the background to be some other video. how do you do something like that, do i need to film somebody in front of a green screen then how do i delete the background and paste that over another video?

[edDV]

Google "Chroma Key"

here is a start
http://www.kenstone.net/fcp_homepage/chroma_key_part_1.html

Green usually works better than blue for consumer camcorders.
Best paint/fabric products to use are optimized for performance and worth the extra price.

http://shop.store.yahoo.com/cinemasupplies/chromkeyfab.html

Rosco paint is the best.
http://shop.store.yahoo.com/cinemasupplies/roschromkeyg.html

[Cornucopia]

Basic Summary goes like this:

Shoot Background

Shoot Actors/Foreground with Green or Blue Background.
For best effect, background MUST be SOLID, EVENLY LIT, SEAMLESS, SUPERSATURATED and UNTEXTURED.

Best colors are specialty green or blue (often "Ultimatte") not available at regular paint/hardware stores, but available from B&H or Markertek among others. Choice of Green or Blue depends on colors of foreground material--you want what is most complimentary (opposite on color wheel/spectrum) to them. Used to be blue, often green these days. Can actually be ANY color (remember it must be opposite the foreground or you'll have "holes" in your foreground).
Green used because it has best dynamic range with YUV mode sensitity.

In video editing app, put Background video on VideoTrack1, Foreground (w/GreenScreen) on VideoTrack2 (above/infront 1).
Apply "Chromakey" or "Matte" or "Alpha" effect. (Might be a 3rd party plugin, names vary with editing app)
Effect will swap particular color with transparency level, adjustable by level of transparency, high of keyed color, etc. Better effects have multiple graduated levels of transparency, and "garbage matte", choke and halo controls, not just a threshold level (ON or OFF). Export a composite of the 2 tracks to a new track. That's it. (Read editing app manual on how to do this best)

Perfection of the effect involves previsualizing the fore- and backgrounds, and matching their perspectives and lighting sources, using a small rim light on the back of your foreground actors, with a compliment to the screen color--better to define your rim edges. If you're shooting video and not film, you can overexpose your background to blow it out/clip the levels--this may help to even the smoothness/solidness of the background.

HTH,

Scott

[edDV]

....

Perfection of the effect involves previsualizing the fore- and backgrounds, and matching their perspectives and lighting sources, using a small rim light on the back of your foreground actors, with a compliment to the screen color--better to define your rim edges. If you're shooting video and not film, you can overexpose your background to blow it out/clip the levels--this may help to even the smoothness/solidness of the background.

HTH,

Scott

Yep the killer is any green reflection (aka spill light) on your forground actors/objects. The main way to avoid this is to put some distance between the actor and the green screen but you need to balance this with lens zoom or you will need a larger green screen and so on. Lots of tricks to the trade.

Neadless to say, shooting a full person is much more difficult than just a head shot over background.

I highly recommend green as the color and avoid similar colors in the forground. YUV cameras are highly sensitive to green and poor with blue and red. Red is close to flesh tones. Blue requires RGB or film source for best sensitivity.

If using a 4:1:1 or 4:2:0 DV cam for forground, Ultimatte guys told me to capture as analog to smooth the edge chroma. Analog or 4:2:2 cams do better for forground. DV capture is fine for the background.

[Cornucopia]

Good tips, forgot to mention the 4:1:1 / 4:2:0 thing.

Scott

[Redd]

Some inexpensive good tools http://fxhome.com/chromanator/.
I love chromakey. I use all the time.