One of the workshops I'm running this year, with colleagues Dave Young and Disa McLean, is on how to chromakey with a Mac.
I had my first play around yesterday and it is soooooo easy using iMovie HD.
To make this video I took a video of a blue lunch box lid against the carpet, then used chromakey to make it mask a picture of my daughter. I was thinking you could use something like this as a guessing game with younger students. Or you could even video a blue square on a student's shirt and turn them into a Teletubby!
To get started I downloaded the plug in for iMovie from Stupendous Software, you have to put the plugin in the right place. You can find the link for downloading and view a visual on where to put the plugin on this page of the workshop wiki.
I put it in my user name > library > iMovie > plug-ins
Now you're ready. To build a movie the first step is to film against a blue screen. Make sure you have a good light source and no shadows. You can film an object moving across the blue screen or, like my movie above, film the blue screen that will be the frame for what image you put behind. Place this movie in your timeline.
Next place the object that you would like to be shown in place of the blue area on your video next to the video in the timeline. I used a still image however you could also use a video. Make sure this video or still image is the same length or longer than the blue screen video.
Next click on the blue screen video and from the editing tab click on video FX and scroll down and click on the one called 'ss Blue Screen, Smooth'. You can move the sliders to get just the right amount of colour and coverage and then select apply.
Once the clip has finished rendering preview to see if it is what you wanted then you can delete the second clip in the timeline as it has been merged with the first.
And there you have it. Blue screening made simple.
You can get the links, examples and explanations on the workshop wiki which is currently under construction.
This was so much fun. If any of my schools out there would like me to come and do a workshop with them, let me know.