A camera captures a photograph in a fraction of a second, but many creative opportunities open up when you manually control the shutter speed. Getting luscious photos of star trails, for example, requires keeping the shutter open for longer than most camera controls allow. To get that shot, you need to switch to Bulb mode and use a manual-release cable to open and close the shutter with the help of a newfangled technology called "your thumb."
Of course, we're talking about photography, so there are plenty of devices and gadgets that give you this and many other options. An intervalometer, for example, fires the camera's shutter at a steady rate over a period of time.
Instead of toting several devices for different shutter speeds, you can turn to your iPhone, iPad, or iPod touch and the free app TriggerTrap Mobile. The app offers numerous ways to control your camera's shutter, provided your camera is one of the hundreds that are supported. The app requires a cable that works with your camera (not all models use the same type of connector), available as a separate $30 purchase.
As a simple cable release, TriggerTrap Mobile is definitely overkill, but in the best way. Four cable release modes let you fire the shutter with a single tap on the app's giant red shutter button, by pressing and holding the button, by pressing once to open and pressing again to close the shutter, and by setting a specific timed release.
But the app gets decidedly more interesting with its Timelapse and Sensor modes.
The Bramping mode sets the number of shots and the interval between shots, but you also get to choose different shutter durations for the beginning and end of the shoot. As daylight fades, longer exposures make better use of available light. Or consider the DistanceLapse feature, which takes advantage of the device's geolocation sensor to take a picture at distance intervals, such as every 500 meters.
TriggerTrap's Sensor modes fire the shutter based on sound, vibration, motion, or facial recognition picked up by the iOS device's sensors and camera. In my testing, I set up my DSLR and an iPhone 5s to capture birds at a bird feeder. The Motion Sensor mode uses the iPhone's camera, so I had to make sure it was pointed at the same spot. The mode doesn't offer a sensitivity setting, resulting in some photos of the bird feeder shifting in the wind, but compensates with a setting to choose how many objects move in the frame before triggering the shutter.
The app's reliance on the iOS device's sensors is also a weakness: it's battery intensive. A screen-dimming option certainly helps in that regard, but if you're going to have it active for a long time, attach a battery pack of some sort.
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