From the article, featured in their special Film Issue:
“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.”
Read the whole review HERE.