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So How Does This All Work?

So How Does This All Work?

Alpha video in Flash 8 is now available thanks to the incorporation of the On2 VP6 video codec in Flash Player 8. In addition to offering a huge increase in quality over the old Sorensen codec, On2 VP6 enables you to encode an 8-bit alpha channel directly into FLV files.

Users familiar with video editing will know that creating alpha channels is a fairly straightforward process. Any popular video editing application can do this, such as Adobe After Effects, Apple Final Cut Pro, and the Avid suite of products. With the Flash Video Encoder (which works with any of these products), creating alpha channels is as simple as selecting a check box during export to incorporate your alpha channel.

Shooting Alpha Video for Dummies

Green- and blue-screen technology is widely used in film and video for keying (short for chroma keying)—the process of extracting a specific color range from a video and replacing that color with transparency (alpha). This technique is commonly used to insert stock footage into a background or composite two scenes into one. To do this, you shoot video against a green- or blue-screen background and then remove it easily in the editing environment.

This process has been around for years in the movie and TV industries but only recently has it become accessible to the general public. When prepping a video for keying, it is important to keep the following in mind:

  • Shoot the video against a solid green- or blue-screen background. Consistent use of that color is critical.
  • Use a high-quality video camera if possible. Video captured with a webcam, for example, can be very difficult to key because of the high level of visual noise. MiniDV is more difficult to key than higher quality, lower compression formats.
  • Know your camera. Because every camera is different, find out what settings it has before you start filming. Here are a few questions to keep in mind when doing this:

    • Does your camera have white-balance controls?
    • Does it have autofocus?
    • Does it have any color-enhancement settings you can use?

    For example, in a test shoot our character had a nice orange color before we started shooting it against a solid blue background. However, in our first attempt at filming, the character turned red and the blue background turned dull gray. So, if you can, lock your white balance before shooting. Refer to your owner’s manual to achieve the best results you can. This applies to locking your camera’s focus too. For a quick result, place a test object on the screen, find the perfect focus level, and then lock it. Or just turn off the autofocus feature altogether and focus manually.

  • Light your set and characters properly. In general, you have more control over your lighting in a studio setting. However, you can also shoot in an area that has a solid light source, such as floodlights or outdoors.
  • Shoot lots of video. Video shoots are usually costly and time-consuming to set up, so always film more than you think you’ll need. You can always edit it down later. Reshooting scenes later may be difficult.
  • Keep notes. Because you will want to shoot lots of video, take notes of the time indexes of nice-looking shots. Notes don’t have to be full of details; just take down the minutes and seconds where the clip starts.
  • Test, test, and then test again. We all do this when programming, so why not apply that to video? Take some time for test shots—the more time you can spend testing, the better. Bring five-second shots into your video editing program and see how the colors turn out, and how easy it is to remove the background from your video. If it doesn’t look right, change some settings and try again.

Ultimately if your project requires high-quality video, you will most likely need to hire professional studio and video personnel to film your video for you. If this option is not available, then rent some professional video equipment and set up your shoot in your basement or back room, where you can control the environment the best. For experimental work, you should be able to get away with a consumer camcorder and some bright reading lights.