Tracking Falling Objects for Slow Motion Video

Falling objects are a staple of slow motion videos, however, they can make problematic subjects. I’ve made a rig that can track small objects as they fall.

In TV advertising, there is an awful lot of slow motion footage. When I mention this to people, they often are doubtful about this, but I'll give you a few examples you see so often that you probably don't notice them

  • Cereal falling into a bowl
  • Fruit falling into yoghurt
  • Chocolate running in ribbons
  • A chef tossing ingredients into a bowl.
  • Coins falling.

Yep, you've seen them all, and I've been on shoots for them all, many, many times. You really haven't lived until you've watch a pineapple explode for the 20th time and it's 3:00am.

Anyway, most of these shots are made at from 500 to 1000 fps (frames per second). To remind you, normal speed video is shot at 24 or 25 fps, so this is 20 to 40 times real time.

At these speeds the human hand is rather too slow to be able to accurately track a falling object if the shot is at all close up, and a camera with a large lens is also to heavy to move fast enough.

The result of this is that the majority of such shots are static and shot a bit wide, so that the action, that is, the object falling through frame, lasts long enough to for the eye to appreciate it. Sometimes we put the camera on its side to get the longer sideways dimension, (1920 vs 1080) but one still only gets two frame heights worth of drop.

So I decided to try to make a rig that allows tracking of falling objects even in extreme close up.
Basically, it consists of two front surface mirrors arranged in a periscope configuration, with one of the mirrors controlled by a servo that is in turn controlled by a computer.

Here's a video of it on YouTube.