Time-Lapse Calculator

1. Enter how long you will keep shooting, in minutes.
2. Enter the interval between photos, in seconds.
3. Choose the playback frame rate for the final video.
4. Read the number of frames, the clip length and the storage needed.

A time-lapse is a video made from many still photos taken at set intervals, then played back at normal speed. Because each frame captures a moment seconds or minutes apart, slow changes such as a sunset, moving clouds or a busy street speed up dramatically on screen.

The trick to planning one is balancing three numbers: how long you shoot, how often you take a photo, and the playback frame rate. Together they set how many frames you capture and how long the final clip runs. Get those numbers wrong and you either fill a card and drain a battery for a clip that lasts a couple of seconds, or shoot far too few frames for the smooth, flowing motion that makes a good time-lapse worth watching.

1. Turn the shoot length into seconds.
2. Divide by the interval for the number of frames.
3. Divide the frames by the playback frame rate for the clip length.
4. Multiply the frames by the average file size for storage.

A longer shoot or a shorter interval gives more frames and a longer clip; a higher frame rate makes the same frames play back faster.

You shoot a sunset for 60 minutes, taking a photo every 3 seconds. That is 3600 seconds divided by 3, or 1200 frames. Played back at 30 frames per second, the clip runs 40 seconds. At 25 MB per RAW file the storage is about 30 gigabytes. Lengthen the interval to 6 seconds and you halve both the frames and the clip length, which is often the easiest way to keep a long shoot within a single memory card and one battery. It is worth running these numbers before you head out, because the shoot time for a decent clip is almost always longer than beginners expect: even a modest forty-second video swallows the best part of an hour on location once you allow for the interval between frames.

Interval

A shorter interval gives more frames and smoother motion, but more storage and a longer clip.

Shoot Length

Shooting longer captures more of the change and more frames.

Frame Rate

A higher playback rate makes the clip shorter and smoother for the same frames.

Subject Speed

Fast subjects such as traffic want a short interval; slow ones such as stars want a long one.

Suggested intervals for common time-lapse subjects.

As a rule, faster subjects need shorter intervals so the motion looks smooth rather than jumpy.

Planning a Shoot

Work out how long to shoot to get the clip length you want.

Setting an Interval

Balance smooth motion against storage and shoot time.

Checking Storage

Make sure your card has room for all the frames before you start.

1. Too Long an Interval

A big gap between frames makes the motion jump; shorten it for smooth movement.

2. Running Out of Card

RAW frames add up fast; check the storage before a long shoot.

3. Forgetting Battery

Long shoots drain batteries; plan spares or external power.

4. Wrong Frame Rate

Pick the playback rate first, since it sets how long your frames will run.

The frame and clip maths is exact for the interval and rate you enter. Storage is an estimate that depends on your file size.

Divide the shoot length in seconds by the interval for the number of frames, then divide the frames by the playback frame rate for the clip length.

At 30 frames per second you need 900 frames. Multiply by your interval to find the shoot time; at 3 seconds that is 45 minutes.

It depends on the subject: 1 to 2 seconds for traffic, 3 to 5 for clouds and sunsets, and 15 to 40 seconds for the sun or stars.

Divide the number of frames by the playback frame rate. 1200 frames at 30 fps plays back in 40 seconds.

Multiply the frames by the file size. 1200 RAW frames at 25 MB each is about 30 gigabytes.

24 fps looks cinematic, 30 fps is standard and smooth, and 60 fps is very smooth. Pick it before you shoot, as it sets the clip length.

The interval is too long for the subject speed. Shorten it so consecutive frames show smaller changes.

Many cameras have one built in; otherwise an external intervalometer triggers the shutter at your chosen interval.

No. The calculator runs entirely in your browser and nothing you enter is stored or sent anywhere.

• Time-lapse photography (Wikipedia).
• Frame rate (Wikipedia).
• Intervalometer (Wikipedia).