Intervalometer

An intervalometer is a device which counts intervals of time. Such devices commonly are used to signal, in accurate time intervals, the operation of some other device. For instance, an intervalometer might activate something every 30 seconds. Other names include interval meter and interval timer.

In photography, intervalometers are used to trigger exposures. This is often done for a time-lapse series. It may also be used to take, or begin taking, picture(s) after a set delay.

Examples of intervalometer use in aerial photography include delaying the start of picture taking by an unattended camera until some time after takeoff and separating multiple exposures in time, and thus distance as the vehicle containing the camera travels, to obtain the 3D effect (stereoscopy). To obtain the 3D effect each image should have about 60% of the surface in common with either the preceding or following image. The interval is calculated as a function of the altitude and speed of the vehicle; shorter intervals for low altitude and high speed.

Often the purpose of a photographic intervalometer is to reduce the resources required either to take the pictures or post-process them as similar images could be obtained by having the camera continuously take pictures as rapidly as possible. Using an intervalometer permits restricting the pictures taken to only those with the desired content. This reduces the requirements for resources such as power and storage media (e.g. film or memory card space).

Most Digital Single Lens Reflex (DSLR) cameras are limited to 30 second or shorter exposures. An intervalometer can be used to take long (>30 seconds) or very long exposures (minutes or hours) using the "Bulb" setting. Long and very long exposures taken at night can be combined to create timelapse animations, star trails, or using astrophotography processing techniques to create images of objects in the night sky like nebulae and galaxies.

Most modern cameras include the most basic intervalometer functionality, the "self-timer". This delays the shutter release for a short time, allowing the photographer to get into the picture, for example.

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