Here’s what it said to do, and it worked: After rendering into a QuickTime/h.264 file, open it up in QuickTime and select “Show Movie Properties.” Highlight the video track then click on the “Visual Settings” tab. Towards the bottom left you should see “Transparency” with a drop-down box next to it. Select “Blend” from the menu then move the “Transparency Level” slider to 100%. Choose “Straight Alpha” from the same drop-down and close the properties window and finally “Save.”
Thanks, Brian. Doing what you suggested does seem to help, though I am finding that dynamics are by no means an exact science. I guess that’s why they’re… dynamic.