The New Diminishing Returns by Mike Powers

EFFECT: You display the fronts and backs of a deck of cards to the audience. A spectator simply names any card they like. You remove the named card and set it aside face-up. You now spread the deck on the table. Somehow all the cards have shrunk to mini size (half as big)! The selected card is still normal size. Then, just when the audience catches their breath, the entire deck grows back to normal size. But, amazingly, the selected card has now shrunk to mini-size! To finish, the selected (named) card visibly grows back to normal size.