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The top-right example uses luminance to determine the transparency in the mask. The white area is completely transparent. Since white is made up of 100% values of red, green, and blue (255,255, and 255), those three colors are all 33% transparent as well. In the lower-right example, blue is the selected transparent index. The blue area is 100% transparent and so are all areas that have a value of 255 for blue (0,0,255), including white (255,255,255).

Chroma keying

Chroma keying or bluescreening is a special case of overlay transparency. A color key is a specific color or a range of similar colors in an image that are made transparent, allowing a background video to show through. The idea is to take a video subject and film it against a solid, uniform background color. It is critical that the color be smooth and uniformly lit with no shadows, and that the color chosen for the background not be used in the subject.

The most important factors in successful blue screening

 

happen during shooting, well before the footage is imported

Magnified

into Vegas software. Compression of the source video is

area

also an important consideration. While almost all video is

 

compressed in some way, highly compressed video does not

 

key well because colors can be smeared together and edges

 

tend to not be very sharp.

 

If your source footage is good and the captured video file is

 

also of high quality, color keying is an easy process.

Uncompressed video

1. Insert a video with a blue (or any solid colored)

 

background into a track. This is the overlay video.

Compressed video

2.Insert the background video that will show through the blue areas into the next lower track.

Note: You do not need to set the lower track as a child track when using the Chroma Keyer plug-in as you would with a mask.

3.Click the overlay video (foreground, higher track) to select it.

4.Drag a Chroma Keyer plug-in from the Video FX window onto the overlay video. The Video Event FX window displays.

5.Click the down arrow to the left of the Split Screen View button () on the Video Preview window and choose FX Bypassed. This will bypass the effect of the Chroma Keyer plug-in until you are ready to view the effect.

USING VIDEO FX, COMPOSITING, AND MASKS

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