Why is this here?
It has been well documented that DV camcorders can be very difficult to use for chroma keying. This section of the site is designed to help newer DV users understand what the problems are and to offer some solutions.

Important Note: This green screen section specifically relates to miniDV and DVcam formats that digitally record video using 4:1:1 color sampling. This information is not applicable to Digital S, Digibeta or other professional formats.

So, what's the problem?
Basically, NTSC DV camcorders use 4:1:1 color sampling when compressing video onto DV tape. In simple terms, this means that out of every four pixels resolved only 1 is being sampled for color. Click HERE to read an explanation by FX pro John Carey. To see the 4:1:1 color sampling in action, go to John Beale's Sony TRV900 Website (John's site is excellent, and I recommend it if you have any interest in DV). The net effect is that chromakeying DV footage often yields large square blocks around your foreground subject. See the screen shots below for an interesting look at a DV frame.

A Closer Look
Basically, these are frames taken directly from DV footage and then modified in Photoshop. Shot 1 has been converted to gray scale. This frame really shows how much more information the DV signal contains in the Luminance portion of the video. In shot 2, I've simply upped the Green portion of the image by a substantial amount. Shot 3 has been hue and saturation adjusted to provide another interesting look at the artifacting.

   

Solutions
The good news is that there ARE solutions for compositing DV. From what I can tell, Adobe After Effects 6 Production Bundle is probably the best out-of-box solution. I captured some greenscreen video through my firewire port using Adobe Premiere Pro and then composited that footage using AE and the results were fantastic. This is due to the awesome KeyLight keying filter that is bundled into AE 6 Pro. After Effects 6 Pro runs about a grand at retail and there are probably more affordable student versions as well. Considering that other professional compositing plugins can cost upwards of $1500, AE's price seems like a bargain. Here are some screen shots that were created with ceiling lights, a reading lamp, green poster board and a 1CCD camcorder:

     
     

Click HERE to download a split screen MPEG2 video of a composite.

www.dvgarage.com offers DV Matte Pro for a reasonable price, though you still must have Final Cut Pro or After Effects 5.5 or later. This plugin appears to do a pretty decent job and they have a demo you can download.

You can also try Earl Thurston's technique, as described on his excellent web site. Earl also does a good job of describing the 4:1:1 color sampling scheme.

Another solution I've used in the past is to capture the DV greenscreen footage by means of an analog capture device, using as little compression as possible (6:1 MJPEG will work fine). Video captured this way does not exhibit the sqare blockiness of native DV video files. Of course this is a trade off, since you'll lose some overall quality when capturing the analog signal. Still, if your keying software just refuses to work with native DV, this option can get your project moving forward. I used Boris FX 3.5 to achieve some pretty good composites a few years ago using analog captured footage, so I know this can work, even with not-cutting-edge compositing tools.

Conclusion
Thanks to advances in keying software, it appears that the days of "tricking" our software into compositing DV footage might finally be gone. Using a tool like AE 6 Pro, you can now get a clean composite without having to resort to choking down the matte until edge detail is gone. You don't need a $1500 plugin anymore to work with less than perfectly shot footage. Independent media creators can finally look past the technology of their favorite affordable video format and concentrate on content.

If you have access to some of the next generation software tools discussed here and have not studied the art of lighting for greenscreen, I would recommend that as a next step. After all, even HD or Film sourced green/bluescreen footage will be difficult to work with if the lighting is poor.

Here are some additional resources that may be of interest:

Chromakey Article
Dummies article with lighting schematic
Blue/Greenscreen Tips

I have a short tutorial for using After Effects HERE.
And of course, some of the books featured in the right column are excellent.