LOL VFX: Phone screen replacement

There’s a scene in the film where Keely and Jaz are sat at the bus stop and Jaz whips out her mobile phone. Keely’s reluctant, but Jaz takes a shot of the pair of them making pouty faces. She then sends the picture as an MMS to Dawber.

It’s 8.30am Sunday morning. We’re ahead of schedule, but still got to squeeze in an extra scene at the bus stop that we missed yesterday. Need to shoot a close up of Jaz’s mobile phone, sending the picture she’s just taken to Dawber. Easy, right? Turns out, it’s really fiddly to compose an MMS on that handset and the owner of the phone doesn’t know how to send a picture message. Time is ticking. What do we do? We shoot the phone with the plain photo on the screen, the plan being to add the caption in post.

Here comes After Effects to the rescue. Straightforward enough to overlay a fake phone screen onto a handset, though two things made it difficult. One, Bryony’s thumb moves over the screen, so it has to be masked out, frame by frame. Two, muggins here decided to shoot the entire film handheld. Sure, it might look nice, but it’s a bloody nightmare for VFX work.

Solution? Motion tracking! I setup two motion trackers on opposite corners of the screen the tracked the movement of the phone, pixel by pixel. That way, when the new display is overlaid, it moves perfectly in time with the footage, and creates the illusion of reality. Took me a couple of hours to create the effect and render it in HD – but I think the end result is pretty seamless. See before and after video below: