Introduction
You're setting up a camera on a rooftop to capture a sunset-to-night transition for a documentary's B-roll. The director wants a 10-second clip at 24fps in the final cut, and the event will unfold over 90 minutes. You need to know the exact shooting interval between frames so the motion feels smooth and the clip length hits the mark. Set the interval too long, and the clouds jump. Set it too short, and you burn through cards and batteries on frames you'll never use.
The time-lapse calculator determines the ideal interval between frames, the total number of frames captured, and the resulting clip length from your event duration and target output.
What This Tool Calculates
The calculator accepts four inputs: total event duration (how long the real-world event lasts), playback frame rate (the fps of your editing timeline), desired clip length (how long the final clip should be in the edit), and shooting interval (the time between each captured frame).
You can solve for any one of these four values by providing the other three. The primary outputs are the shooting interval in seconds, total number of frames captured, total clip duration at your playback frame rate, and the effective speed-up factor.
The Formula and How It Works
The core formula is: Total Frames = Event Duration / Interval. The clip length equals Total Frames divided by the Playback FPS.
To solve for the interval when you know your desired clip length: Interval = Event Duration / (Clip Length times Playback FPS).
Worked example: You want a 10-second clip at 24fps from a 90-minute sunset. Total frames needed = 10 times 24 = 240 frames. Interval = 90 minutes / 240 frames = 5400 seconds / 240 = 22.5 seconds between each frame.
The speed-up factor equals Event Duration / Clip Duration = 5400 / 10 = 540x. The sunset will appear to happen 540 times faster than real life.
For smooth motion in time-lapse, a general guideline is to keep the shutter speed at roughly half the interval or longer. At a 22.5-second interval, a 10 to 15-second exposure (using an ND filter) produces natural motion blur in clouds and traffic, while a fast 1/100 shutter speed at the same interval produces sharp but jumpy individual frames.
Real-World Examples
Sunset to Night Skyline for Documentary
A documentary crew set up a Sony A7R V on a rooftop to capture a 2-hour sunset-to-twilight transition. The editor requested a 12-second clip at 24fps. The calculator returned an interval of 25 seconds and 288 total frames. The crew configured the intervalometer and set the camera to aperture priority mode with auto-ISO to handle the 8-stop brightness change from daylight to city lights. Total storage used was approximately 14 GB of RAW files.
Construction Site Progress Over 6 Months
An architecture firm documented an office building construction with a weatherproof camera shooting one frame every 10 minutes during daylight hours (12 hours per day) for 180 days. The calculator showed 180 times 72 = 12,960 total frames. At 24fps playback, the final clip ran 9 minutes. The firm trimmed it to a 3-minute highlight reel using every third frame, which the calculator confirmed by recalculating at a 30-minute effective interval.
Star Trail Sequence for Narrative Film
A feature film's second unit shot a star trail time-lapse over 4 hours in the Mojave Desert. They needed a 6-second clip at 24fps (144 frames). The calculator returned a 100-second interval. The DP chose a 90-second exposure at f/2.8, ISO 3200 on a Canon R5, leaving 10 seconds between exposures for buffer write time. The continuous long exposures produced smooth star trails without gaps between frames.
Recommended Intervals by Subject
| Subject | Interval | Speed-Up Factor (24fps) | Notes |
|---|---|---|---|
| Fast clouds | 1 to 3 sec | 24 to 72x | Short interval for smooth rolling motion |
| Sunset / sunrise | 10 to 30 sec | 240 to 720x | Match interval to rate of light change |
| City traffic | 2 to 5 sec | 48 to 120x | Shorter intervals show individual car streaks |
| Star movement | 15 to 30 sec | 360 to 720x | Match exposure length to interval |
| Plant growth | 5 to 15 min | 7200 to 21600x | Requires fixed lighting and stable mount |
| Construction | 5 to 30 min | 7200 to 43200x | Weather protection required for camera |
Pro Tips and Common Mistakes
Pro Tips
- Use a longer shutter speed (half the interval or more) to introduce motion blur into each frame. This smooths the playback and eliminates the staccato look that plagues time-lapses shot with fast shutter speeds.
- For sunset and sunrise time-lapses, shoot in manual mode with auto-ISO, or use a dedicated ramping device like the Alpine Labs Radian 2. Without exposure ramping, the brightness shift causes visible flicker between frames.
- Calculate your battery life before you start. A Sony A7 series camera typically lasts roughly 2,000 to 3,000 actuations on one battery. A 6-hour time-lapse at 10-second intervals is 2,160 frames. Bring at least 2 batteries.
- Shoot RAW, not JPEG. The ability to batch-correct white balance and exposure across thousands of frames in Lightroom or Camera RAW eliminates flicker far more effectively than any post-processing deflicker plugin.
Common Mistakes
- Setting the interval shorter than the camera's buffer write time. If your camera takes 3 seconds to write a RAW file to the card and you set a 2-second interval, you'll miss frames. Always test your write speed before committing to an interval.
- Not locking focus to manual. Autofocus during a time-lapse causes the lens to hunt between frames, creating subtle but visible focus shifts in playback that are impossible to fix in post.
- Forgetting to disable image stabilization. On a tripod, IBIS or lens stabilization can introduce micro-movements between frames as the system resets between captures. Turn it off for any tripod-mounted time-lapse.
Frequently Asked Questions
How long should my time-lapse interval be for a 30-second clip?
It depends on the event duration. At 24fps, a 30-second clip needs 720 frames. Divide your event duration by 720 to get the interval. For a 1-hour event: 3600 / 720 = 5-second interval. For a 6-hour event: 21600 / 720 = 30-second interval.
Can I change the interval mid-shoot?
Technically yes, but it changes the speed-up factor mid-clip, which looks jarring in playback. If you need to change interval (such as speeding up as the sun rises), use a ramping intervalometer that smoothly transitions between intervals over a set number of frames.
How do I avoid flicker in my time-lapse?
Flicker comes from slight exposure variations between frames. Shoot in full manual mode (including ISO). Avoid apertures smaller than f/8, because the aperture blade position varies slightly between actuations on most lenses. Use electronic shutter if available. In post, apply a deflicker plugin like LRTimelapse or GBDeflicker.
What is the difference between a time-lapse and a hyperlapse?
A time-lapse captures frames from a fixed camera position. A hyperlapse moves the camera a measured distance between each frame, creating a traveling effect. The interval and clip length calculations are identical. The hyperlapse adds the complexity of maintaining consistent movement increments and stable framing between each captured frame.
Start Calculating
Time-lapse photography compresses hours into seconds, turning invisible processes into compelling visual stories. The math is simple, but getting the interval right before you press the shutter button means the difference between a usable clip and a wasted shoot day.
Run your next time-lapse through the calculator above, save the interval and frame count, and set your intervalometer before you leave the camera unattended. What subjects have you shot as time-lapses, and what interval worked best?
