People these days have short attention-spans, so although time-lapse videos can be very appealing, most of us would probably prefer to watch one for 30 seconds rather than ten minutes. Thanks to a clever feature which Apple simply refers to as “dynamically selected intervals,” almost any time-lapse video you shoot in the default Camera app in iOS 8 will end up as 20-40 seconds, whether you shoot for 10 minutes or two hours …
Turns out, what Apple is doing is quite simple, and indeed, pretty clever. What Apple means by “dynamically selected intervals” is they are doubling the speed of the time-lapse and taking half as many pictures per second as the recording duration doubles. Sounds complex, but it’s actually very simple.
Studio Neat compiled the results of their tests into a simple table:
What this means is that a five-minute time-lapse will be captured at two frames a second and end up 20 seconds long at 30fps. A 40-minute time-lapse will be captured at one frame every four seconds and thus also end up 20 seconds long.
You don’t need to know in advance how long your time-lapse will be: the Camera app will automatically switch frame-rates as the recording time increases, dropping frames from earlier sections to match.