The iPhone’s Quad-LED True Tone flash is pretty good as camera flashes go, but you should never use it to take actual photos, unless you want shiny-faced, red-eyed people in your portraits. Instead, you should put it to work in more useful applications. And no, we don’t just mean using it as a flashlight next time you take a trip into the basement.
Silent Flash Alerts
First off is a simple, built-in trick that means you’ll never miss an alert again. The ‘LED Flash for Alerts’ feature does just that, flashing the iPhone’s lamp whenever you get an alert that would usually produce a sound. You can use it instead of sound, or use both sound and flash together. The flash is powerful enough to shine through a jeans pocket, and is great for getting your attention in a noisy environment. And if you are hearing-impaired, you may find it essential.
To enable it, you just head to Settings>General>Accessibility>LED Flash for Alerts and toggle the setting on, like this:
One thing to remember: the flash keeps working even when your iPhone is set to silent using the mute switch. It is, however, disabled in Do Not Disturb mode. In short, it works any time the vibrating alert would work.
Take your pulse
There is a whole section of the App Store where you’ll find apps that can measure your heart rate using the iPhone’s LED. In principle, it works just like the little monitors that doctors clamp onto your fingertip to monitor your pulse. It’s called pulse oximetry, and it works because each pump of your heart delivers fresh, oxygenated blood which is redder than the de-oxygenated blood it replaces. The color difference can be measured with a camera, and the iPhone’s camera is more than up to the task.
To use these apps, you place a finger over the camera lens, and the flash lights up to illuminate the blood in your fingertip. I tested Runtastic’s Heart Rate app against old-fashioned counting with a stopwatch and the results matched. You can also hook the app up to Apple Health to track your results over time. It’s no Apple Watch, but it’s accurate and easy.
Musicians — good ones anyway — use a metronome to practice. Following the click helps you to develop a good sense of rhythm, and it’s essential for staying accurate as you develop speed on your instrument. Most metronome apps come with a feature that will flash the LED lamp in time with the clicks. I like Soundbrenner’s Metronome app. You can even turn off the sound and use the flash only, which is handy if you don’t want to annoy the other people in your home, or if you’re recording and don’t want the click on your track.
Change brightness with 3D Touch
If you own an iPhone 6s or later, you can use 3D Touch to change the brightness of the LED lamp. Just swipe up to bring up the Control Center form the bottom of the screen, and Force Touch on the flashlight button. This brings up a little menu with options for Bright (the default), Medium, and Low Light. This setting is persistent, so if you pick the Low Light, the low setting is retained the next time you activate the light.
This is especially handy if you’re using the light to light up a room, or a tent, or anything else that requires leaving it lit for a while. For this post, I tested the battery drain of the LED on full power. It dropped from 97% to 81% over an hour and a bit (1 hour 14 minutes to be exact). That’s not too and, but it isn’t nothing. Lowering the light levels will help reduce that drain.
Bonus tip: Catch mosquitoes
Nope, I’m not kidding. The iPhone makes a great mozzie catcher. Next time you’re awoken by the menacing high-pitched whine of nature’s most hated insect in your ear, pull out your iPhone and go to work. Flip on the lamp (on the low setting if you can — see below), and hold it up to the wall, around an inch away. What you’re aiming for is a small, bright patch of light. The mosquito will soon be tempted into the light, whereupon you can extinguish its worthless existence. Oh, it helps to have a fly-swat handy too. A book or a magazine creates a gust of air that can sweep a tiny insect to safety.
Whatever you do, though, don’t whack it with your iPhone, no matter how sleepy you are.