Time-Lapse Interval Calculator

The Math Behind Motion: Time-Lapse Interval Calculation

The Time-Lapse Interval Calculator serves to bridge the gap between real-world time and the final cinematic sequence. A time-lapse condenses a long duration (like hours) into a short clip (like seconds). To achieve the desired playback speed and clip length, a photographer must precisely calculate the delay, or interval, between each photograph. This guide explains the core principles and calculation.

1. Determining Total Required Frames

The first and most critical step is determining the total number of frames the final video clip needs. This is based purely on the desired outcome: the clip's duration and the chosen playback frame rate (FPS).

Total Frames=Clip Length (s)×Frame Rate (fps)

For example, to create a 10-second clip at the standard cinematic rate of 24fps: 10 seconds×24 frames/second=240 frames. This is the total number of photos you must take.

2. Calculating the Optimal Interval

Once the required number of frames is known, the calculation determines how often the camera must capture a picture to spread those frames evenly over the total shooting duration. The entire shooting duration must first be converted into seconds for an accurate result.

Interval (s)=Total FramesTotal Shooting Time (s)​

If you plan to shoot for 2 hours (7,200 seconds) and need 240 frames, the interval is: 7,200 seconds÷240 frames=30 seconds. Therefore, the camera must take one photo every 30 seconds.

3. Practical Considerations and "The Bulb Ramper"

Understanding the interval is crucial for setting your camera's intervalometer. If the calculated interval is shorter than your camera’s exposure time (e.g., the camera needs 4 seconds to take a photo, but the calculated interval is 2 seconds), you must adjust your desired clip length or shooting duration. The calculator ensures that your planning is precise, preventing footage that is too fast or too slow, which would require complex editing fixes later.