Gone are the days when it seemed like you had to be a math major to do all the calculating it took to produce an acceptable image. Digital technology does so much that even the pros are inclined to just set it and forget it. Remote triggers take this hands-off approach a step further by allowing you to press the shutter button while you're away from the camera -- or maybe even in the shot yourself. You can also set up series of flashes remotely, using each other to set off a chain of flashes that can light a photo creatively and in ways that wouldn't be possible using just one flash.
Wired triggers use wires to close an electrical shutter switch or fire the flash. Wireless camera and flash triggers use radio waves to set off flash units and cameras located in different areas. Creating homemade triggers is a common hobby for photographers, and instructions abound on the Internet for making remote triggers out of old cell phones, walkie-talkies and even doorbells.
While one of the main uses of remote triggers is in long exposures, such as those occuring in astrophotography, there are certainly other ways action photographers can make use of a remote trigger. A remote trigger allows photographers to get shots from locations that aren't accessible in real time. Using clamps, photographers can attach cameras to specific locations and then trigger the camera when the subject moves near the frame. Action photographers use remote relay flashes and cameras at races, for example, to follow the action around the track. Nature photographers also love remote cameras for capturing animals in unguarded moments. A camera rigged to a backyard birdfeeder can collect fascinating shots.
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