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CHROMA KEYING

Multimedia II. CHROMA KEYING. How it works. Greenscreen / bluescreen Every time you watch the weather Combines two video images into a single picture

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CHROMA KEYING

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  1. Multimedia II CHROMA KEYING

  2. How it works • Greenscreen/bluescreen • Every time you watch the weather • Combines two video images into a single picture • Designates a single narrowly defined color in one image and electronically replaces that color with a second image leaving the rest of the picture untouched http://www.wikihow.com/Chroma-Key-in-Windows-Movie-Maker

  3. How it works (continued) • Place a foreground subject in front of a chromakey color (usually bright blue or green) • Feed the picture through one channel of a digital switching system • Feed a background picture through another • Command the system to replace the designated color in the foreground picture with the same areas of the background http://www.videomaker.com/article/3409

  4. Chroma Key • Process is based on the luminance key; everything in the image over (or under) a set brightness level is “keyed” out and replaced by either an image, or a color from a color generator. • Creates keys on just one color channel

  5. Why Blue? • Red, green and blue channels have all been used • Blue has been favored • Complementary color to flesh tone (most common color in scenes is flesh tone, the opposite color is logical to avoid conflicts) • In the past cameras and films have been most sensitive to blue light

  6. Why Green? • Green has advantages as well • Greater flexibility in matting with blue foreground objects • Greater reflectance than blue • Video cameras are most sensitive in the green channel, and often have the least noise (distortion in the video) in that channel http://www.seanet.com/~bradford/blue_green_screen_visual_effects_1.html

  7. Things you will need • Bluescreen or greenscreen (can be as simple as a piece of fabric taped to the wall or wood painted with chroma key paint) • Video camera • Multiple light sources • Windows Movie Maker or other video editing software

  8. RE-CAP • You shoot a video with a single colored backdrop (blue or green is often used) , Movie Maker allows you to make that color transparent – replacing it with any other video clip or still image • You can essentially transport yourself to the moon, your favorite vacation spot, or your favorite film!

  9. Let’s Practice • Create a folder on the M: Drive and name it Greenscreen • Find a video clip or still picture online and save it to this folder (this will be your background) • If time permits we will pair up and shoot footage of each other in front of the “greenscreen” SEE STEPS TO CHROMA KEY HANDOUT

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