I decided to show the progress of software Petzval emulation after the last post 2 years ago! Seriously, a young friend that has helped me shoot photos for years had this on her website. Conclusion? A lot of youth like the retro look, but don't know what they're looking for. If you'd like to see some real Petzval shots, there are over 2,000 on the Petzval Photographs Flickr group I started back in 2008: http://www.flickr.com/groups/868027@N25/
But Garrett, you can clearly see in the picture that it's a clear-center blur filter. The ring of clarity is quite evident.
"It's the way to educate your eyes. Stare. Pry, listen, eavesdrop. Die knowing something. You are not here long." - Walker Evans
He is no fool who gives what he cannot keep..to gain that which he cannot lose. Jim Elliot, 1949
Woah, crazy to see this old thread pop up again...
It strikes me that these days, the Lytro could be the ideal camera for a very good Petzval modeling plugin. When you have the whole light field, you can do pretty crazy things. Currently they're sort of wasting the potential, as you can only emulate a "perfect" wide aperture lens, which is a little boring. But theoretically you could use any lens design to introduce its specific "defects" and character.
They should really get on that, right after they do autofocus video