HERE is another Chroma Key tutorial.

Pay close attention to the Parent/Child reference. I found that to be very helpful.

The tutorials are a good resource. Search the web for more. Also, search YouTube -- I know there are some examples there.

A very basic (simplified) workflow would be:

1. Apply the Chromakey effect to your clip.

2. With the Chromakey effect disabled (unchecked) in the Video FX chain, click on the chromakey eyedropper, then click and drag a representative, rectangular sample of your background (greenscreen? bluescreen?) in the preview window.

3. Now re-enable the chromakey in the effects chain, but in the chromakey FX window tick the "Show mask only" option.

4. Now drag the "High Threshold" slider down (to the left) until all of your subject shows as solid white. If it looks grey, it will be transparent.

5. Now drag the "Low Threshold" slider to the right until all of your background in the preview window turns black. But don't let it affect your solid-white subject.

6. Add a slight amount of blur (in the Chromakey window) to smooth the edges of your subject.

7. Finally, untick the "Show mask only" box.

Adding a little bit of Chromablur effect ahead of the Chromakey effect can also help smooth the jaggies, especially for DV video sources.

If you still have trouble, you might have to improve your lighting. Be particularly careful when shooting to not let the subject get too close to the background -- make sure you don't get shadows on the background. Also, adding some rim-lighting on the subject may help.

Tim L

I just my first extended chroma key test in VMSP7 -- which is actually a music video for Gigi Dover's "Crazy Molly" now up on YouTube -- and totally learned as I went. We shot against a poorly lit $40 10x24 green muslin sheet bought online from a video supply shop. Everything was poorly lit, and we were actually going for the grainy lo-fi look you see onscreen...but in a few places I fought the chroma key effect boundaries until...I discovered the magic chroma Key color selection 3 color "sliders". I like to work with the effects at the track level to keep automation simple (for me, anyway), so click on the chroma key effect and 1. use the eyedropper and select a rectangle of the BG color that's going to be chroma keyed out. 2. when you get to a frame that's beginning to lose the CK effect, drop back into this parameter and fiddle with:
a. the min and max settings -- these are extremely important, and interactive, and will take a bit of getting used to and....
b. try moving one or more of the RGB value "sliders" up or down the scale just a bit. I found this will often cure the CK malady better than the min/max adjustments. They're all interactive, and I'm sure that the signal parameters of the scene are changing just enough to throw my initial setting out of kilter.
Voila! Automation to the rescue!!

Doing this project was so much fun that I'm definitely going to be using this feature a lot, even in non-"special effects" videos, just to compose my shot more easily.
Mojo