Time lapse formula
Every time-lapse is a balance of four numbers: the interval between shots, the shooting duration, the frame rate of the final video, and the clip length. Photo count is shooting time divided by the interval, rounded to the nearest whole photo. That is the same count common time-lapse calculators use. An intervalometer that also fires at the exact end time can record one extra frame.
- Number of photos = shooting duration ÷ interval
- Clip length = number of photos ÷ fps
- Interval = shooting duration ÷ (clip length × fps)
- Shooting duration = number of photos × interval
- Speed-up = interval × fps
- Storage = number of photos × file size per photo
Example
You want a 20-second sunset clip at 25 fps. That is 500 frames. If the sunset takes 1 hour (3,600 s), the interval is 3,600 ÷ 500 = 7.2 seconds. At 25 MB per RAW file you need 12.5 GB of card space (1 GB = 1,000 MB).
Recommended intervals
| Subject | Interval |
|---|---|
| Fast clouds, traffic, crowds | 1–3 s |
| Sunset / sunrise | 3–10 s |
| Slow clouds, shadows moving | 5–15 s |
| Night sky, Milky Way, star trails | 15–30 s (exposure + 1–2 s) |
| Plants growing, construction | 5–30 min |
For night shots the interval must be longer than the exposure plus the camera's write time. With a 20-second exposure, use an interval of at least 22 seconds.
FPS for a time-lapse
24 fps gives a cinematic look. 25 fps is the PAL/European standard and 30 fps is the US/NTSC standard. Higher rates such as 50 or 60 fps look smoother but need more photos for the same clip length. If you are unsure, match the frame rate of the rest of your video project.
Shooting tips
- Use manual exposure, manual focus, and a fixed white balance to avoid flicker. For day-to-night transitions, use aperture priority with a holy-grail ramping tool.
- Turn off image stabilisation when the camera is on a tripod.
- Shoot RAW if you will grade the footage, or JPEG to save space for very long sequences.
- Use an intervalometer or your camera's built-in interval timer. Check the battery: thousands of shots can drain it.
- Shoot about 10% more frames than you need so you can trim the start and end.
Planning a long time-lapse
For multi-day projects such as construction, plant growth, or seasons, work backwards from the clip you want. A 60-second video at 30 fps needs 1,800 frames. Spread over 30 days of daylight-only shooting (12 hours a day), that is 1,800 frames across 1,296,000 seconds, so one photo every 12 minutes exactly. Use Interval mode here, or the interval calculator, then check storage so the card or drive is big enough. Use mains power and weatherproof housing for long outdoor setups.
Frequently asked questions
How many photos do I need for a 10-second time-lapse?
At 24 fps you need 240 photos, at 25 fps 250, and at 30 fps 300.
What interval should I use for a sunset time-lapse?
Usually 3 to 10 seconds. A 5-second interval over one hour gives 720 frames, which is 28.8 seconds of video at 25 fps. For a clip length you choose, use the interval calculator.
How long do I need to shoot for a 30-second clip?
At 25 fps a 30-second clip is 750 frames. At a 5-second interval that is 3,750 seconds, or 1 hour 2 minutes 30 seconds.
How much storage does a time-lapse need?
Multiply the number of photos by the file size. 1,000 RAW files at 25 MB each need 25 GB. The storage calculator also shows how many hours fit on a card.
What is the speed-up factor?
It is how much faster than real time the clip plays: interval times fps. A 5-second interval at 25 fps is 125 times real time.
How often does a time-lapse take a photo?
As often as the interval you set. A 5-second interval takes one photo every 5 seconds.