Every new camera sold today has some sort of light meter built in. Its purpose is to read the scene you’re composing and, if you’re shooting on the dreaded “Auto” mode, tell the camera how to correctly expose the photograph. If you’re shooting in aperture priority, shutter priority or — god bless you — full manual mode, that meter tells you if your shot is over- or underexposed so you can adjust accordingly. Integrated light meters are indispensable for on-the-go shooting, but for portrait, still-life or landscape photography where you have more time to compose the image, a hand-held light meter is still the way to go to dial in a perfect exposure. Photography, by definition, is the capturing of the light bouncing off of a subject. So it makes sense that getting your meter as close to your subject will produce a more accurate reading.
When it comes to buying a handheld light meter, you can go full-on old school with an analog needle-reading meter or spring for a highly accurate digital model. Now there’s a third option, Lumu ($149), an innovative new light meter that works with something you already have in your pocket — a smartphone. Lumu is one of those elegantly simple gadgets that looks as if it could have been designed by Apple itself. It’s no bigger than a stack of coins, plugging into the headphone jack of a smartphone and working in tandem with a free companion app. Lumu’s diminutive size is perhaps its greatest strength, but also its weakness — it’s pretty easy to lose. But Lumu compensates by providing a fold-over leather case and a neck lanyard so it can be worn like an amulet, pegging you as a member of the photo tribe.
Lumu couldn’t be easier to use, even if you have no experience with a hand-held light meter. Just plug it in, making sure the white light sensor is facing your camera. Then hold the meter up next to your subject, whether that’s your five-year-old kid, your favorite timepiece or your vintage Corvette, and click “Measure”. The app immediately displays the correct aperture and shutter speed required to expose the photo properly. By clicking on any of the parameters, you can lock it and Lumu will tell you how to set the others. For example, if you’re shooting at ISO 400 and your desired aperture is f/8, the Lumu will spit out the proper shutter speed. Set your camera and shoot.
Lumu is equally useful for digital or film photography, even if your camera has a built-in light meter, which includes most that have been sold in the past 40 years. Of course, with digital cameras, you can always look at the LCD after every shot and adjust (or not if you’re shooting RAW). But Lumu is particularly handy for those who still shoot film, in an ironic mashup of old and new technologies. In my long-term testing of the Lumu, we found it to be highly accurate for dialing in proper exposure. Once we learned to trust it more than my camera’s meter, I relied on it for aperture and shutter speed settings almost exclusively, minimizing guesswork.
Still, the convenient little light meter is not without its flaws. Since Lumu is designed for use in ambient light, it isn’t really useful for flash or studio photography. Also, it doesn’t work well with thick or tight-fitting smartphone cases, since the meter itself sits fairly low on the stalk. And at $149, it isn’t exactly cheap. But for the shooter looking for a way to elevate his film or digital game, or the photographer who simply can’t have enough gear, Lumu is money well spent.