For this effect to look realistic, obviously the clock’s second–hand must be made to move. However, because we are recording Sarah’s entrance three different times — once for each visible version of her personality — making certain the moving second–hand is in the correct position for each pass would have been nearly impossible.

The first “second–hand” solution that comes to mind? Physically remove the clock’s second-hand and replace it with a special effect. But here is where we run into trouble. You see, one of the challenges of working on a shoestring budget is that you must borrow rather than buy props. Our wall clock was on loan. As such snapping off that little red second–hand simply wasn’t an option. Instead I removed the clock’s battery and manually positioned the second–hand where it’d do the least amount of damage to the shot. With all the clock’s hands now in fixed positions we recorded the three passes of Sarah entering the waiting room.

In post–production our challenge is to merge the three versions of this shot into a seamless whole while at the same time preserving all the reflections and shadows from the original imagery. To achieve this goal, animated masks had to be hand drawn around each of the three versions of Sarah as she entered the room. Furthermore, the original second–hand had to be painted out and replaced with an artificially generated second–hand.

I hope you’ll agree that the effect turned out reasonably well; right down to the little bounce of a real second–hand at the end of each movement.

The only other alternative, and also the option we chose to use, is to shoot without a green screen. Instead, during post–production, an animated mask was hand drawn around each of the overlapping on–screen characters. At thirty frames per second and hundreds of mask points per frame, you can easily imagine why building the film’s effects took several weeks to complete.