When you're done, go to the Chaos Collective's Make Your Own DOF-Changeable Image page and choose the file you just created. After a few moments, you'll see your video transformed into a still image that you can click to change the focus. It seems magical.
Afterwards, you can click the upload and share link to post your creation to Twitter, Facebook, and elsewhere so other people can click around in your photo as well.
This should work in any browser, but I have had the most success viewing these images in Chrome. Here is the variable-focus version of a photo I shot on the Santa Monica Promenade.
Sign up for MIS Asia eNewsletters.