An intervalometer is a timer that fires the camera’s shutter automatically at set intervals, or holds it open for precise durations. It can take a frame every few seconds for hours, or open the shutter for an exact number of minutes, removing the need to stand there pressing a button. Many cameras now include one in the menu, and external versions plug into the remote port or trigger wirelessly.
Its most familiar use is time-lapse, where the camera captures one frame at a regular interval, say every five seconds, across a long period, and the frames are later played back as video to compress hours into seconds. The intervalometer controls the interval, the number of shots, and when the sequence starts. One firm rule governs the interval: it must be longer than the exposure plus the time the camera needs to write each file, or frames will be skipped.
The same tool drives a hyperlapse, where the camera is moved a set distance between frames, and more advanced workflows ramp exposure across a sequence to handle the huge brightness change from day to night, a technique known as the holy grail time-lapse. Software then deflickers the result so the brightness transitions smoothly.
The second key use is exposures longer than the camera’s built-in limit. Cameras typically cap their timed shutter speed at 30 seconds, so anything longer requires bulb mode, and an intervalometer can hold bulb open for an exact two, five, or ten minutes without you touching the camera. This is essential for deep long exposure photography with strong ND filters.
Intervalometers are also how photographers build light trails and star trail images. Rather than one enormous exposure, they shoot a long sequence of shorter frames back to back, which are then stacked in software into a single image showing the full arc of star motion or traffic. This approach is common in astrophotography because it keeps noise low and salvages the sequence if one frame is ruined by a passing car or plane.
Setting one up means choosing the interval, the exposure length, the number of frames, and any start delay, then letting the camera work unattended on a solid tripod. A bonus benefit is steadiness, since firing the shutter without a finger press removes vibration, much like a self-timer but repeatable across hundreds of frames. For long runs, an external power source or battery grip is worth having, because a dead battery ends the sequence.
A first time-lapse is the best way to learn the tool. Pick a scene with obvious motion such as moving clouds or a busy street, set an interval of a few seconds, shoot a few hundred frames, and assemble them into video. The result makes the relationship between interval, frame count, and final clip length immediately clear.