Now, we’ve taken care of all the settings for panning and zooming but we still haven’t actually executed the key to make the blue background transparent. Since this file has no clean plate, we will do this manually. First, click on the Keyer tab so that you can access the keyer tools. Now, select the Add Key Point tool (the first one under the input clip window) and click on several representative points in the backing color. Each of these will turn to a white square. Now, in the Keyer control panel, click on the Apply Points button; this will calculate a color range for the matte and the backing color will turn transparent.
If you’ve picked a good set of Key Points, the initial results will be pretty good. However, be aware that ULTRA CS3 is at its best with 60i talking heads; it does not handle motion blur very well, so 24p action shots with lots of motion blur will be problematic. You’ll probably see that there is a blue glow around the girl from the initial settings, which is worse in the frames where her arm moves quickly and is blurred. Try increasing the transparency a bit, then adjust the Shrink Matte and Spill Suppression to get rid of the glow and spill and get as close to a clean composite as possible. Now click on Save Output (in the Output panel) to render the file.
I was able to create a clean composite for the entire file except for the motion blur around the model’s left hand as it extends out from the body both times, where there is some blue around the fingers.
The tutorial lets you see both the strengths and weaknesses of ULTRA CS3. For corporate, news, or news magazine type shows with a virtual set, ULTRA CS3 is hard to beat for the price. For filmmaking where there will be a lot of action it is less ideal, and another choice such as zMatte or Primatte might be better.
(Printed with permission from Focal Press, a division of Elsevier. Copyright
2007.
"Bluescreen Compositing: A Practical Guide to Video and Moviemaking" by John Jackman. For more information about this book, please visit: http://www.focalpress.com.)
