How is this done? - Halftone transition ("On Type with Erik Spiekermann")
One of my favorite pieces of animation, Creativity Explained: On Type with Erik Spiekermann (Oddfellows)

I love the transition that happens between 0:26 - 0:29. How would I go about replicating this sort of animation? I have an idea about an expression or two that might be used, but can't quite figure out the rest. Anybody out there know how something like this is done?
Appreciate any direction/thoughts, thank you!
