What this calculator does
Time-lapse has three numbers and people usually pick the wrong one to start from. The instinct is to choose an interval, shoot, and find out afterwards that two hours of work produced eleven seconds of footage. The better order is to decide how long the clip should run and let that choose the interval.
The relationship is unforgiving. Two hours shot at five second intervals gives 1,440 frames, which at 24 frames a second is exactly one minute of video. Stretch the interval to fifteen seconds and the same two hours gives twenty seconds.
The formula
The number of frames is the event length divided by the interval. Playing them back at the frame rate gives clip length = frames ÷ frame rate. Running that backwards gives the interval you need for a target clip: interval = event length ÷ (target × frame rate). Card space is simply the frame count times the file size, which is where raw files become a planning problem rather than a quality choice.
| Term | Meaning |
|---|---|
| Interval | Seconds between shots. The one setting that decides everything else. |
| Frame rate | Playback speed of the finished clip, not the camera's burst rate. |
| Compression ratio | How much real time fits into a second of footage. |
| Integration | Not used here. Time-lapse frames are separate exposures rather than stacked ones. |
The inputs explained
| Field | What to enter |
|---|---|
| Length of the event (min) | How long the event actually runs, in minutes. A sunset is twenty to forty; a construction day is eight hours. |
| Interval between shots (s) | Seconds between shots. Two to five for traffic and people, fifteen to thirty for cloud, much longer for construction. |
| Playback frame rate (fps) | The frame rate of the finished clip. 24 is cinematic, 30 and 60 are smoother and need proportionally more frames. |
| Average file size per shot (MB) | Average file size per frame. Raw files on a modern camera run 25 to 60 MB, JPEGs far less. |
| Clip length you want (s) | How long you want the finished clip to run, used to work the interval backwards. |
When to use it
Planning backwards from a clip length
Decide the clip should run twenty seconds, enter it as the target, and the calculator gives the interval. For a two hour event at 24 fps that is fifteen seconds between shots, which is a very different shoot from a five second interval.
Checking you have the card space
A two hour lapse at five second intervals in raw is 1,440 frames and about 35 GB. Shooting that onto a 32 GB card means running out roughly fifteen minutes before the end, which is the sort of thing worth knowing beforehand.
Matching the interval to the subject
The compression ratio output tells you how much real time is squeezed into each second of footage. Fast subjects want a low ratio and slow ones want a high one, and a cloudscape at 120 to 1 looks about right while traffic at the same ratio is unwatchable.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What clip length does each interval give?
Only the interval between shots changes.
| Interval | Clip length | Shots needed | Card space |
|---|---|---|---|
| 1 s | 5:00 | 7,200 | 175.8 GB |
| 2 s | 2:30 | 3,600 | 87.9 GB |
| 5 s | 1:00 | 1,440 | 35.2 GB |
| 10 s | 30.0 s | 720 | 17.6 GB |
| 15 s | 20.0 s | 480 | 11.7 GB |
| 30 s | 10.0 s | 240 | 5.9 GB |
How does the frame rate change the requirement?
The shooting is identical. Only the playback frame rate changes.
| Frame rate | Clip length | Interval for your target clip | Real time squeezed into the clip |
|---|---|---|---|
| 12 fps | 2:00 | 30.0 s | 60:1 |
| 24 fps | 1:00 | 15.0 s | 120:1 |
| 25 fps | 57.6 s | 14.4 s | 125:1 |
| 30 fps | 48.0 s | 12.0 s | 150:1 |
| 60 fps | 24.0 s | 6.0 s | 300:1 |
Questions
What interval should I use?
It depends entirely on how fast the subject moves. One to three seconds for people and traffic, five to fifteen for cloud and shadow, thirty or more for construction and plants. The compression ratio output is a better guide than the interval itself.
Why is my clip so short?
Because frames are consumed quickly. At 24 fps a minute of footage needs 1,440 frames, so an hour of shooting at ten second intervals produces fifteen seconds. Work backwards from the clip length instead.
Should I shoot raw or JPEG?
A choice between quality and card space, and this page quantifies the trade. Raw at 25 MB across 1,440 frames is 35 GB; JPEG at 8 MB is 11. For a long lapse the shutter count matters too.
Does the interval include the exposure time?
On most cameras the interval is measured between shot starts, so an exposure longer than the interval will make the camera skip frames. Keep the interval comfortably longer than the shutter speed.
What about holy grail transitions?
Day to night lapses need the exposure to change during the shoot, which this does not model. The frame count and clip length arithmetic is the same either way.
For the exposure side of a long shoot see ND filter exposure, and for storage across a whole job photo shoot storage. Video bitrate and file size are on video file size.