Time-Lapse Calculator

A time-lapse compresses hours or days into seconds of video: clouds racing over mountains, a city waking up, a flower opening, a building rising. Getting it right depends on one relationship: how often you take a photo, how long the event lasts, and how long the finished clip should be. This calculator works it out either way, along with storage and shutter speed.

The core equation

Number of photos equals event length divided by interval. Clip length equals number of photos divided by video frame rate. Knowing any two of interval, event length and clip length gives the third. A sunset of 90 minutes shot every 5 seconds gives 1080 photos, a 43-second clip at 25 fps or 36 seconds at 30 fps.

Two ways to plan

“I know the interval” is for when the subject dictates the timing, for example fast clouds. The calculator tells you how long the clip will be. “I know the clip length” is for when you need, say, a 15-second sequence for a video edit. It tells you how often to shoot.

Choosing an interval

Fast-moving subjects need short intervals, or the motion looks jerky. As starting points: fast clouds and traffic about 2 seconds, sunsets and slow clouds 5, moving shadows and crowds 15, star motion 30, plants growing 10 minutes, construction projects 30 minutes. The presets fill these in.

Frame rate

24 fps gives a cinematic feel, 25 fps is standard in PAL regions and Europe, 30 fps in NTSC regions and on most social platforms, and 60 fps gives very smooth playback but needs twice the photos for the same clip length.

Storage and actuations

Enter the size of one photo, 20 to 60 MB for RAW, 5 to 15 MB for JPEG, and the calculator totals the storage. Long projects add up quickly: a week-long construction time-lapse with a photo every 10 minutes is about 1000 photos, while a night of 30-second stars can fill a card. The number of shutter actuations is shown as well, worth knowing since mechanical shutters have a finite life; electronic shutters avoid that wear.

Smooth motion: the 180-degree rule

Very short exposures give a staccato look in time-lapses. Filmmakers aim for an exposure about half the interval, the 180-degree shutter rule, which creates natural motion blur. For a 5-second interval, that is about 2.5 seconds, which in daylight needs an ND filter; the ND Filter Calculator gives the strength.

Practical tips

Use manual exposure, white balance and focus to avoid flicker from frame to frame. Use a sturdy tripod and protect it from wind. For day-to-night transitions, “holy grail” techniques gradually adjust exposure; shoot raw for room to correct. Bring spare batteries or external power for long sessions.

Editing the frames

Import the photos as an image sequence into a video editor, which most offer. Crop to 16:9 or vertical 9:16 for the target platform; a 24-megapixel photo gives plenty of room to crop a 4K frame and even to add a slow digital pan.

Related tools

Plan the timing of sunrises, sunsets and golden hour with the Sun Angle Calculator. For star trail sessions, use the Star Trail Calculator. To turn photos into a short animation, try the GIF Maker.