On Apple’s website, they claim that in time-lapse mode, “iOS 8 does all the work, snapping photos at dynamically selected intervals.” When I first read this, I thought they were doing something super fancy, like monitoring the frame for movement and only snapping a picture when something changes. On deeper reflection, this would be a bad idea. Time-lapse videos look best when they are buttery smooth, and dynamically selecting intervals in this fashion would create a jittery and jerky video. So what does Apple mean by “dynamically selected intervals”?
Turns out, what Apple is doing in quite simple, and indeed, pretty clever.