Time-Lapse Interval Guide: Frames, FPS and Clip Length
How interval, frame rate, shoot time and clip length connect, with intervals for clouds, sunsets and stars and how to plan a shoot both ways.
The four numbers and how they link
A time-lapse is governed by just four figures: the interval between frames, the playback frame rate, the real-world shooting time and the finished clip length. They are tied together by two small equations. Frames equal the shooting time divided by the interval, and the clip length equals those frames divided by the frame rate. Fix any three and the fourth is decided, which is why this tool lets you solve from a shoot you plan to do or backward from a clip you want to end up with.
Picking an interval for the scene
The interval is the single biggest creative choice, because it sets how compressed time feels. Fast subjects need short intervals so motion stays smooth: 1 to 2 seconds for scudding clouds or busy traffic, 2 to 3 seconds for a bustling street. Slower subjects tolerate long gaps: 15 to 30 seconds reads well for a sunset, 20 to 60 seconds for drifting weather, and several minutes for stars, tides or a growing plant. Too short an interval buries you in near-identical frames, while too long a gap makes the result stutter.
Planning backward from the clip you want
Editors often start from the delivery, not the shoot. Say the edit needs a 10 second establishing shot at 24 fps. Switch to the 'From clip length' tab, enter 10 seconds and 24 fps, and the tool shows 240 frames. Add your interval and it reveals the shoot time, so a 2 second interval means 8 minutes on location, while a 30 second interval means two hours. Seeing that before you set up tells you whether the shot fits the light, the battery and the schedule you actually have.
Watching for rounding and drift
Two rounding rules matter in practice. Shooting from a duration floors the frame count, so any time that does not divide evenly by the interval is discarded, which can leave the clip a hair short of the round number you pictured. Solving from a clip length rounds the frames to the nearest whole frame instead. On long shoots also remember that real intervals drift a little as the camera writes files and meters exposure, so treat the shoot time as a close plan rather than a stopwatch-exact figure and give yourself a small buffer.