While it’s not as ubiquitous as its cousin slow motion, we’ve all seen time-lapse footage before. Whether it’s a sun and moon racing across the sky, usually signifying the passage of time/tripping one’s balls off, or endless traffic rushing through a busy intersection, often used to convey the bustling activity of an urban environment, the technique pops up frequently in everything from feature films to music videos and TV commercials. It’s usually only a few fleeting moments, an easily forgotten stylistic flourish, and there’s a reason for that, namely that producing time-lapse footage is an expensive, time consuming pain in the ass, and as such it’s not something people give much thought to. But it’s worth taking a moment to break it down, since the principles that make this cinematic effect possible illuminate the technical and physiological underpinnings of the entire medium. And besides, it looks really cool.
Film, at its core, is based on one biological phenomenon known as persistence of vision, which causes any image to be retained by the eye and brain (there’s some debate as to which organ is predominantly responsible) for a fraction of a second, usually cited as 1/25 or 1/30. Its discovery is sometimes attributed roman philosopher Lucretius, but the subject gained a more scientific grounding through experiments with stroboscopic light conducted by British physician Peter Mark Roget in 1824, after which amusements like flip books and zoopraxiscopes, which paved the way for animation by presenting a series of still images just fast enough to be seen as motion, became common. A handful of serendipitous technological innovations, from a handful of kooky inventors, made it possible to do the same with photographs, and film was born. The (average) human eye begins to perceive fluid motion at around 16 frames a second, but 24 soon became standard.
Exploring their new tools, inspired filmmakers, largely following the lead of movie magician Georges Méliès, explored the possibilities of using frame rate as a special effect. Back then, movie cameras were clunky, hand-cranked affairs, and if a director or cinematographer wanted to slow something down, they would spin the film through faster, getting more exposures per second, which, played back at a normal speed, appeared as one motion unfolding at a glacial pace. Appropriately, they called it overcranking, and the opposite was, predictably, undercranking, where a cameraman slows the exposure rate down, only capturing one image every second, so when it was projected at 24 frames a second, the subject looks sped up. The thing is, slow motion can also be easily achieved by slowing down regularly shot footage, but it doesn’t work the other way; to speed up one long action, you’d have to use costly stock film on the whole thing, and then wastefully compress it.
Filming, or perhaps more accurately photographing, at that pace, obviously takes a lot of time and produces little footage, which is why you see time-lapse used so sparingly. The ordinary economics of movie making stress getting as much on film as you can in as little time as possible (craft service ain’t cheap!), but it looks so interesting that filmmakers and advertisers justify the expense for a little zazz here and there. It’s often worth the effort however, since there’s really nothing else that looks quite like it. There’s often a strange, otherworldly feel to time-lapse imagery, as if it’s somehow a recreation of reality in addition to just a photographic representation of it, at once contrived and hyper real. There are those who employ it as mindless flash, but when it fits with the other aesthetic and thematic elements, time-lapse can be quite effective (the end of Spike Jonze’s Adaptation springs to mind).
Though historically its technical complexity has kept it from being used as extensively as slow motion, the rise of digital photography has been a game change for time lapse. Gigabytes of memory are much less expensive the rolls of film and can be used over and over again, so that even amateurs with normal consumer electronics can easily get started making their own time-lapse videos with a little initiative. In the hands of professionals however, the rapidly advancing technology has allowed an age-old technique to take on new levels of depth and reality, in part by letting photographers go over their work frame by frame and correct exposure inconsistencies and the slight blur caused by the camera shutter. Alongside improvements in slow motion, with ever more sophisticated high-speed cameras, we’re increasingly able to see our world in ways that we never have before. Vision isn’t the only thing so persistent.