Hong Life CalculatorsUnderstanding the time-lapse calculator — concept and principle
A time-lapse turns hours of real time into seconds of video by taking photos at regular intervals. This calculator works out how many photos you will take, how long the resulting clip will be, how much faster than real time it plays and how much storage you need. It can also find the interval needed for a clip of a set length.
How it is calculated
Photos = ⌊scene duration (s) ÷ interval⌋ + 1
Clip length = photos ÷ frame rate
Speed-up = interval × frame rate
Storage = photos × photo size
For a set clip length: photos = ⌈clip length × frame rate⌉; interval = scene duration ÷ (photos − 1)
The principle
Each photo becomes one frame of video. The camera takes the first photo at the start and then one every interval, so the count is the duration divided by the interval plus one. Played at the video frame rate, those frames last photos ÷ fps seconds. Every second of video contains fps frames, each separated by one interval of real time, so time on screen runs interval × fps times faster than reality.
Worked example
Default inputs: scene 2 hours, interval 5 s, 30 fps, photo size 25 MB.
- Scene duration = 2 × 3,600 = 7,200 s.
- Photos = 7,200 ÷ 5 + 1 = 1,441.
- Clip length = 1,441 ÷ 30 = 48 seconds (0:00:48); interval 5 s.
- Speed-up = 5 × 30 = 150×.
- Storage = 1,441 × 25 MB = 36.02 GB.
| Shooting interval (seconds) | Photos to take |
|---|---|
| 1.25 | 5,761 |
| 2.5 | 2,881 |
| 3.75 | 1,921 |
| 5 | 1,441 |
| 6.25 | 1,153 |
| 7.5 | 961 |
| 10 | 721 |
How to read the result
Fast-moving subjects like traffic or crowds suit short intervals, and slow processes like sunsets, star trails or plant growth suit longer ones. Check that your memory card has space for all photos with a margin and that the battery will last; long night shoots often need external power. Shooting in RAW gives more editing latitude but uses much more storage.
Common mistakes
- Forgetting the extra first photo, which changes the count by one.
- Choosing an interval shorter than the exposure plus camera processing time.
- Running out of battery or card space partway through.
- Letting auto exposure flicker between frames; manual settings often give smoother results.
Frequently asked questions
How long a clip do I get from 1 hour at 5 s intervals?
721 photos, about 24 seconds at 30 fps.
Why is my clip shorter at 60 fps?
The same photos are played twice as fast, so the clip lasts half as long.
How do I avoid flicker?
Use manual exposure, white balance and focus, or deflicker in editing.
Sources: Arithmetic of frame sampling: frames = duration ÷ interval + 1; clip length = frames ÷ frame rate; storage = frames × file size