How to control your camera from your smartphone or tablet

Triggertrap

Triggertrap Mobile is £23 from triggertrap.com. The companion app is available free for iOS and Android. The kit includes a dongle that plugs into the smartphone or tablet, and a detachable cable designed for specific camera models. Additional cables are available for £7.

^ Triggertrap Mobile connects your phone’s headphone socket to your camera’s wired remote input, and is available for a wide range of cameras

Triggertrap is most likely to be used with the camera mounted on a tripod. The cable isn’t particularly long, though, so you might need to think about how to support the smartphone. Triggertrap Phonetrap, £15, is a cradle that sits in the camera’s accessory shoe. Another option is an iKlip Mini, which is around £21 and is designed to attach a smartphone to a microphone stand. We made do by slinging our phone’s wallet-style case around the camera’s neck strap – not the most elegant solution but it did the job.

^ Triggertrap in action, using the phone’s case to suspend it from the camera strap

The Triggertrap app has a dizzying list of shooting modes. The simplest takes a photo when you press the big red button on the app. There’s also a simple self-timer mode, albeit with the option to set the time interval from milliseconds to hours.

The next three modes are for cameras that support bulb mode, where the shutter stays open for as long as the trigger signal is received. You can press and hold the app’s button to set the shutter speed manually, or tap to open and again to close. A third option is to specify the shutter speed in the app. This is useful for very long exposures beyond the usual 30 or 60 second limit imposed by the camera, but where you want to control the exposure level carefully – perhaps for night-time photography or when using an ND filter to blur out moving subjects.

On the subject of ND filters, at the bottom of the list of shooting modes is an ND calculator. Enter the ND filter strength and the base shutter speed (the shutter speed you would use without the filter) and the app tells you what shutter speed to use to get the same exposure with the filter fitted. There’s also a Solar Calculator that gives the sunrise and sunset times for your current location.

The app’s Timelapse section includes five modes. Timelapse is the simplest, whereby you simply set the interval between shots. In TimeWarp mode, you set the total duration and number of shots, and draw a curve to create a varying frequency of shots. This creates a time-lapse sequence that gets faster and slower over time. A steeper incline in the curve means fewer photos will be captured, so time will speed up when playing back as a video with a fixed frame rate.

^ TriggerTrap’s TimeWarp mode varies the frequency of shots in a time-lapse sequence

DistanceLap uses the smartphone’s built-in GPS to capture a photo every set number of metres. That’s ideal for time-lapse sequences taken from a moving vehicle where you want the animation to progress at a constant speed, regardless of whether the vehicle had to start and stop.

Star Trail mode uses the bulb mode to create a sequence of exposures lasting minutes or even hours. It’s also possible to specify the gap between exposures. It’s worth keeping a close eye on your kit when using this feature for all types of time-lapse where a long exposure is used. Some cameras are ready to take another photo pretty quickly, but others take a long time to apply noise reduction and save the file after capturing a long exposure.

Bramping mode is short for bulb ramping. With the camera set to bulb mode, it’s possible to vary the shutter speed throughout the duration of the time-lapse. You enter the interval, number of exposures and start and end shutter speeds. This makes it possible to capture time-lapses with a varying exposure – perfect for sunsets and sunrises. The fastest shutter speed available is 1/15s, but even that might be too fast for the camera to respond to accurately in bulb mode. It’s best to do some test runs and monitor the results before going out and using the feature properly.

^ TriggerTrap’s Bramping mode uses the cameras’ bulb mode to vary the shutter speed

Another limitation is that the Triggertrap app increases the shutter speed in a linear fashion. For example, if you ask it to capture ten frames with shutter speeds varying from one to ten seconds, the shutter speeds used will be one, two, three seconds and so on up to ten. However, our eyes perceive light exponentially, so ideally the exposure should increase by a multiplier value rather than a fixed amount between each frame. For example, shutter speeds of 1/2s, 1s, 2s, 4s, 8s and so on would double the exposure each time and give a similar perceived difference from one to the next.

The list of modes doesn’t end there. Long Exposure HDR mode provides a bracketing feature, taking anything from three to 19 frames at varying shutter speeds. Then there’s HDR Timelapse, which uses bracketing and time-lapse functions at the same time.

Sound Sensor mode uses the smartphone’s microphone to trigger the camera when sound passes a set threshold. It’s fun being able to trigger a photo simply by clapping, and could be the perfect way to capture group portraits without having to grapple with Wi-Fi remote triggers or self-timer functions. It might even prove to be effective for capturing fleeting but noisy subjects.

^ Triggertrap can also be used to trigger the camera when the phone’s microphone detects an audio signal

However, there’s some latency to the app’s response. We measured a quarter of a second with the Android app and a tenth of a second for the iOS app. That’s too slow for the split-second accuracy that you’d need for photos of popping balloons, arrows through apples and other high-speed photography techniques.

The iOS (but not the Android) app also includes a mode where photos are triggered from the iOS device’s vibration sensor, plus two modes that use the camera to detect motion or a specified number of faces. The motion sensor is probably the most practical of the three, but we struggled to set the threshold in low light – the algorithm doesn’t appear to differentiate between movement and the fizz of image noise.

Overall, though, Triggertrap Mobile is a superb product that’s cheap to buy and is likely to keep on improving as the app is developed.