There's an effect by Shin Lim called "Flawless" which is an ACR technique.Here it is:
The email continued:
Not a bad idea, per se, but one of the main problems with it is that the double doesn't work well unless the cards are brand new. And even then, it's risky. The bottom side of the double (where you're not gripping) can open, causing a mini-tent effect. Very easy to flash.
What my gripe is, this flaw is IN the demo, in both takes that Shin uses.
So what does Shin do? He momentarily BLURS the video image so the viewer can't see the double is exposed at the bottom! He clearly flashes in both takes, but the blur covers this flash at the obvious point.
I found it rather amusing that Shin couldn't come up with even ONE decent take that has a convincing double in his effect.
Hehe I agree.