The secret of time-lapse video
We’ve all seen them at some point, on TV or in film: gorgeous shots of clouds marching across wide skies or car lights streaking along night-time city streets, condensing huge spans of time into seconds. Time-lapses have been dazzling audiences for decades, but how do they work?
In principle, time-lapse (or “timelapse” or “time lapse” – they all mean the same thing) is simply the process of playing back frames of footage at a faster rate than they were taken. Easy. But first it helps to understand a bit about how regular footage works…
In film circles there are terms like “under-cranking”, which creates the time-lapse effect, and “over-cranking” which creates the slow-motion effect. Both terms comes from the days when camera operators would have to manually turn a handle to crank the film past the camera’s shutter in order to expose it and create footage. If they cranked too fast then the footage would look slow, and vice versa. They seem to have often been slightly too slow, which is why a lot of early film footage looks to be sped up!
Warning: this bit contains geekery…
Let’s get into some numbers. In the UK, TV footage is generally shot at 25 frames per second (fps). This means that a video camera captures 25 images every second and each image represents 1/25th of a second in real-time. When played back at 25fps, the recording and playback speeds match and the effect is that the footage looks like it’s being played in real time. Still with me? Good.
If you play with the relationship between the recording and playback speeds, interesting things happen. Say you have a time-lapse camera taking one picture every minute. In order to capture the number of frames required to create one second of footage, the camera would need to be snapping away for 25 minutes. When played back at normal speed, the video would seem to be condensing 25 minutes of activity into just one second – it’d make 25 minutes look like it’s happening quickly, and that’s how time-lapse video works. High five to you – you just did maths!
Phew! Back to normal
So that’s the technique. With our custom-designed HD and Ultra-HD/4K cameras we can create time-lapse videos that cover events spanning hours through to years.
How is time-lapse best used? Keep checking our blog for some of the best ways to use time-lapse to create spectacular videos.