Lumu Power iPhone light meter review

Lumu Power is an incident light, flash and colour meter that plugs into your iPhone. Is it any good?

Lumu Power

My gosh, has it been 4 years since I saw this little guy for the first time?

I’d always been fascinated with what was the Lumu light meter. Now, the Lumu Power color & light meter. One of those smart companies that must have thought: “Hey, these smartphones have all this processing power, why not create our product to take advantage of it?”

Four years ago, I was really just starting out in my photography career and some very senior colleagues were telling me about how great light meters were. How great it is to point your light meter up to your subject and get a perfect reading to set your camera’s holy trinity: ISO-shutter and aperture. Yes, very cool. Then, you can adjust all your external lighting.

But light meters can be expensive. Nothing to say about color meters! At the time, light meters still had 80’s LCD screens and looked clunky to operate. They probably hadn’t changed much in 10 – 15 years. You could get purely analog versions which were cheaper. But really? You want to use something like that in front of a client in the digital age? If you’re famous old-school, okay. But that’s not 99.9% of us.

A year or two later, light meter models were vastly upgraded to what they basically look like: smartphones with a half-sphere bulb on top of them. The resemblance is undeniable. I still remember to this day what I thought when I saw them: It’s about time! Not only did they look like modern pieces of gear, but the interface looked amazing. A lot of thought went into it that’s for sure.

Coming from an IT career, I’ve always been amazed in the computing power of smartphones. The average consumer has no clue. Millions of times more powerful than NASA’s computer to launch the first spaceship to the moon. So, why don’t companies who need a computing platform simply try to integrate its needs with a smartphone?

Now, we see that much more. Especially with drone controllers. But 4 years ago, there was really nothing. Except for the Lumu light meter. Really, it’s just the sensor that’s going to be custom. The rest is just programming to read the signals from the sensor. While I’m able to describe the process, the reality is much more than that.

Lumu asked Lighting Rumors to evaluate their latest version, Lumu Power, which has flash and color metering as well. It’s tiny! How tiny? I thought I lost it. Even with the cute holding pouch it comes with. It was hiding in plain sight. It’s that small. You can place at 3 of them on an average sized business card.

Lumu Power

I was going to test it using my iPad Pro as my iPhone 5 has a busted camera. My iPad Pro is almost two years old so it should work on an iPhone 6 or newer without any problems I would think.

Software installation is as simple as any iOS software is. Go to the Apple Store and download the Lumu app and start it. Here’s the part that Lumu needs to work on: the interface. I’m not an expert at interface design, but I’ve learned and taught people on hundreds of computer applications and I’m a photographer. It’s not hard. But if you’re not familiar with light meters and how to use them, it can be a bit confusing. After watching a few Youtube videos, I got it and the interface made more sense. Which is why I love the interface on dedicated light meters. It’s extremely simple. That’s my opinion. Now, for the good stuff.

Lumu PowerLumu Power app screenshot

Digital exposure meters start at around $350. Color meters start at $1300 and go over $2000. Where does color metering come into play? I mostly think of product photography. Or if you just want an accurate base setting and move on from there. At least you can saturate colors while still keeping the colors within the realm of accurate. So when you look at $300, it’s starting to show some real value. Of course, you need an iPhone as well.

The app and sensor is impressive. Ambient light readings were right on the money. Perfect. But spot metering wasn’t. I also saw a Youtube video where they also found that out. The app is using the camera on your phone to take that reading. And you know, the camera on your phone isn’t a precision instrument designed for this. And there’s all sorts of software stuff going on too. The Youtuber found about a 1/3 stop difference when metering with a Lumu and dedicated meter. When using the setting with my camera, I did too. Adjust your settings accordingly. Not a big deal.

Lumu Power app screenshot

I took color temperature readings under various lights and adjusted the white balance on my camera accordingly. Have to say, it was damn close if not spot-on! My camera can only adjust its light-temperature settings by 100k increments at a time where the Lumu app makes adjustments at 10k. Readings between the two were extremely close where I could barely see a difference. Barely.

Lumu Power app screenshot

One of the things I initially didn’t test—but my convincing Editor wanted me to try—was the Flash Exposure feature. Honestly, I didn’t think it was that important. Shows you my ignorance about light meters. I’m glad I did!

Lumu Power app screenshot

You can test exposure of your flash/strobe with this feature. You set the shutter and ISO settings and when you trigger and click ‘Start’ on the menu. Then the app waits for the light to trigger. When the light triggers, it will tell you what aperture to use to get proper exposure where the light is hitting your subject. Or you can move the sensor to a different position to get a different reading, thus getting a different look on your image.

Honestly, it also took a while for me to figure out how this work. Not one of the Youtube videos I watched reviewing the Lumu did an adequate job of explaining this feature of it and how to use it. I had to watch Youtube videos of people using traditional light meters! Yes! The old-school crowd! Check out the Adorama video with Mark Wallace. He’s always great.

The $300 question: Is it worth it? In short: Yes. But not necessarily for the reasons you might think:

  1. Speed. I’m pretty good at guessing exposure value. Out in bright sunlight? Use the ‘Sunny 16’ rule: F/16, ISO 100, Shutter 100 – 125. Indoors under ‘regular’ lighting? f/5.6 – f/4, ISO 100, Shutter 100 – 125. So once I get my primarily light source setting correct, I just use ratios to get everything else right. With the meter, there is no guessing. Guess what? Using a rim light with someone with blonde hair is going to meter differently than a brunette.

    Speed. No guessing. Looking much more professional. Honestly, the more a client watches you doing things they don’t understand and you look confident in it, the more professional and authoritative you look. Seriously.

  2. Consistency. What if you have a 2nd shooter on your project? Like a wedding? You can calibrate exposure and color balance (with the chromaticity feature) and color temperature to match each other exactly! Don’t underestimate this. Canon images tend to be heavier on red and Nikon Green. So yes, this is important when you want images to have the same color ‘look’.

  3. Education and Experimentation. Yes! The more I played with this, so many ideas starting flowing through my head. I think as a beginner, this can be a necessary tool in order for you to learn lighting, ratios and setting up your gear appropriately. It’s like learning how to take photos in ‘M’ mode. Yes, it can be hard. But you learn so much more. Once you ‘get it’ with the basics, then going beyond that to create a specific look.

I look at this ordering and find it kind of funny. The first two are geared for the advanced and pro (me) and the 3rd, for the beginner. So there really is something for everyone. There are other features for the app that will appeal to the videographer and geek. But they are above me and would do a disservice trying to explain them. Things like luminance, chromaticity and others…

Example photo by Ricardo Gomez
Lit with flash, metered using the Lumu Power

When I did the first draft without the flash metering testing, I wrote that yes, it’s worth it. But it would be lower on the ladder in the purchase priority. Now? I wish there was a device this affordable when I started in photography. Lighting is everything in photography and a tool like this can help tremendously in understanding it. And for $300? A bargain.

The Lumu Power light meter is available for $299 at

Ricardo Gomez
Ricardo Gomez is a photographer based in New York City who specializes in fashion and portrait photography.