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This brief chromakey tutorial is designed for individuals that may be new to
keying film or video footage. This is by no means comprehensive, but rather
provides a quick overview of the process. This example was created with After
Effects 6 using the Keylight compositing filter and specifically addresses
keying using DV footage, which has presented challenges for some time in the
area of keying. I captured the source video to my computer using Adobe Premiere
Pro's built in DV device control and DV codec. The video was not captured
through analog ports or otherwise modifed before being imported into After
Effects.
The Source Files:
First you need some green or bluescreen footage. In my example, I've shot some
of the worst possible source material ever created for a compositing project.
Bascially, I stuck a piece of bright neon-green construction paper on my wall,
set up my Elura camcorder about 3 feet from the paper and then video taped a
star wars toy moving around in front of the camera. Lighting was provided by my
ceiling fan lights and a 40 watt reading light. Seriously, this is terrible
beyond belief. If I can make this work, just about anything should work.
1.First create a new DV composition in AE and set an image or video as the
background. In this instance, I've used a beautiful picture of the sky that my
wife took.
2. Drop the greenscreen footage on top of the background image.
3. Right-Click the greenscreen video and select the KeyLight filter as shown.
4. KeyLight sets up a default matte as soon as you select a color using the
color picker tool (see arrow). Note that although the key is decent right away
around the front object, there is a lot of "dirt" shimmering through on the
left and far right sides of the video. This is due to the uneven lighting on
the screen, which causes the screen to appear as varying shades of green.
5. Now the matte needs to be tweaked to accomodate the less-than-perfect
screen. Notice in the image below that I"ve modified several of KeyLight's
adjusters, especially the Screen Strength, Screen Balance,
Clip Black and Clip White. I've also adjusted
the Screen Pre-blur and Screen Grow/Shrink in
very small amounts.
6. Once the composite looks pretty good, its a good idea to view the screen
matte directly. From the View button, select Screen Matte to view the actual
matte. I still had some transparency in the foreground object, so I tweaked the
matte a little more at this stage.
7. And here's the final composite (click HERE
for split screen MPEG2 video). Will it trick people into thinking a toy speeder
bike is flying around on a sunny day? Probably not. Is it still pretty
impressive? You bet. Consider this:
KeyLight allowed me to get a fairly good composite using a regular ceiling
light, a 40 watt reading lamp, green poster board, a 1CCD
camcorder, native DV source video and a toy.
In the past, Adobe After Effect's keying capabilities without third party
plugins has frequently been criticized. However, with the introduction of
KeyLight in the production bundle of After Effects 6, I think Adobe has really
vanquished this problem with a vengeance. Lets face it, if it can work with the
pathetic project used for this demo, imagine what it can do for you when you
combine KeyLight with proper lighting, a good green/blue screen and a high
quality camera?
8. Lasly, here are several screen shots that demonstrate how well KeyLight
handles transparency, even with poorly shot DV video:
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