Light meters are essential to my workflow. Shooting with a lot of fully manual film cameras you can save money buy purchasing ones with broken meters. My favorite two cameras, a Leica and Hasselblad, never even came with built in meters. This makes it necessary for me to have one on hand in tough lighting situations like being indoors or cloudy days.
Lumu found a way to cram a light meter it into a something the size of a bottle cap. All you need to do is download the app and then plug it into the headphone cap and you're ready to go. Although everything sounded good I wanted to make sure that it would hold up well along my tried and true Sekonic L-308s.
I did some pretty basic tests, outdoors in the sun, in the shade, further in the shade and indoors. It was surprising that both meters gave really similar readings. Most of the time they readings were exact and when they weren't it was extremely close.
The advantage of the Lumu is that it's so small and convenient. It's also why it can be a liability too, it constantly fell off my phone and I was always worried I was going to lose it. I find myself using it less and less for those reasons. If I'm going on a trip and extra space is a luxury, I'm taking the Lumu but on my normal weekend shoots I have my Sekonic L-308s in my pocket with fresh batteries.
If this helped you and you would like to purchase a light meter use these link for the Sekonic and Lumu. Even if you buy something else like.... a 2018 daily planner to journal your year it helps support this page and my work.