At its most basic form, time lapse photography is any video recording where the frame rate of the capture is much slower than that of the projector. This gives the feeling of faster motion, letting us see things that we wouldn’t normally be able to perceive in the same short period of time. For example, this can be the stars moving across the sky at night-time or the construction of a stadium occurring over several months. The way that this process works is actually quite creative. Below, we’ll look at the basics of the time lapse and how this amazing filming technique is done.
A Question of Speed
When we view a standard movie at the cinema, the images are usually recorded at 24 frames per second (fps). This gives us the usual images that we’re used to with all actors and props being viewed as they normally would with our own two eyes. Now, time lapse occurs when you change the frame rate of the camera recording the event. By capturing fewer frames per second and then playing them back at the regular rate, what you see on the screen will be perceived as moving in a more rapid manner. To give you an idea of how much the motion will be sped up, here are some specific examples:
- A captured frame rate of 12 fps will seem twice as fast when viewed
- A captured frame rate of 6 fps will seem four times as fast when viewed
- A captured frame rate of 1 fps will seem 24 times as fast when viewed
Typically this slower frame rate is achieved with an intervalometer, a device that attaches to and controls the internal shutter mechanisms. This can be a piece of hardware or software depending on the time lapse camera involved. The more complicated gadgets can also involve panning, tilting and more to capture much more complex footage while slowing it down as smoothly as possible.
Dealing with Motion Blur
When filming any kind of time lapse footage, the artist also needs to consider the exposure time when compared to the frame interval. With standard film, the shutter is actually only open for half the interval time (i.e. 1/48 of a second of exposure for a 1/24 frame interval). This short exposure drastically reduces the motion blur, creating the fluid movement we’re used in when at the movie theatre.
For time lapse photography, while a short exposure time will create a sharp image, it also has the effect of producing an end result that looks like stop-animation capture. People and vehicles will hop erratically from one place to another revealing the large gaps of time missing from the footage. A longer exposure time will produce much smoother movements, although overall motion blur will then increase. After all, one frame will contain a lot of information as whatever is being filmed is recorded in multiple positions in the single shot. The true artist will balance these two aspects to produce excellent quality time lapse footage.
In more complicated scenarios, the camera can actually be moved while filming in a slower frame rate. For example, the videographer is in a car recording the street they’re driving down. In reality though, smooth footage requires the use of a motion control rig to pan or tilt the camera at the same speed as the shutter. This will produce a more natural movement even though the footage appears sped up to those watching in the cinema. Despite its complexity, this time lapse method has been used to produce some extraordinary films in the past.