Lumu: A Light Meter For Your Smartphone

I don’t do a lot of gear reviews, in fact, this is my first for Fstoppers (bear with me). But Lumu is a product I’ve been following since it’s launch on Kickstarter back in 2013. I didn’t invest back then, I’ll tell you why later, but it's a great concept that has become a reality so I’m here to give you my honest thoughts and a short video we hacked together using the meter in the field.

Who’s it for

Not a lot of photographers seem to use light meters anymore. Maybe it’s because they’re chimping at the tiny LCD screens on the back of their cameras, or maybe it’s because they’re using histograms, but I still use a light meter regularly. Call me old-fashioned, but I like to know where my lights are in relation to my subject. While I don’t expect Lumu to replace my Sekonic light meter, as a professional photographer, I think that it’s certainly worth having in your travel kit. But more than that, with the popularity of mirrorless cameras and other compact cameras these days, which have a price point much lower than standard DSLRs, a $500 Sekonic meter just doesn’t make sense. That’s where I think the Lumu fits. With anyone who wants a reliable, accurate, ambient light meter without the big price tag of full-featured professional units.

Build Quality 

With a CNC milled high grade aluminum housing, the Lumu comes in either silver or black. While it doesn’t weigh much, it certainly feels like its built well. The company says each piece is assembled and built by hand. Lumu comes with a hand crafted leather case and neck lanyard, which both seem to be on par with the quality of the device itself. Although we didn't drop test it, I think the Lumu would stand up to most normal wear and tear.


At 24mm diameter and 18mm thick, Lumu isn’t going to slow you down. It’s a little smaller than a quarter. What I like most is that it doesn’t even require batteries. There are three apps available for iPhone and Android, Lumu Photo, Lumu Video, and Lumu Pinhole. For my testing we used the Lumu Photo app, although my assistant also used the Lumu Video app and claims it was “surprisingly accurate”. But I’m getting ahead of myself. As I said the Lumu has FREE applications built for the iPhone and Android, which require nothing more than a quick download and to plug the device into the headphone port of your smartphone. Once connection is established, you can easily isolate Aperture, ISO, and shutter speed readings within ambient environments by tapping on one of those three exposure elements to select it, hit the measurement button, and the selected element will adjust based on settings of the other two. For example, if you want to shoot at ISO 50 with an aperture of f/11, simply tap the shutter speed value to select it. Once selected, tap the measure field and watch as the shutter speed field changes to the ambient reading.

How Did It Perform?

I have to say, I was skeptical at how well this thing would perform, considering its a fraction of the size and cost of my professional light meter. The meter is designed for measuring ambient light. This is a limitation with the device which prevented me from investing in the initial Kickstarter campaign. Having said that, it does ambient REALLY well. I mean as good as my Sekonic light meter. Held side-by-side, the Lumu gave exactly the same readings in an ambient light environment as my other device. And even if it was a little off, the iPhone and Android applications even allow you to dial in calibration to exacting specifications.


The only design issue I noted was that Lumu doesn’t work with all smartphone cases. It rests pretty tight against the headphone port, and even the narrow thickness of some cases is enough to cause the device not to establish a connection. As I mentioned, the meter is only intended for ambient readings. As a studio photographer, this was pretty limiting to me, although we do shoot most architecture with just ambient light, with a few hot lights thrown in effect, it still would have been nice to see flash meter functionality with the device. 


At $149 the units seem slightly overpriced for what they do. I would personally like to see the device around $99 bucks. Now before the folks at Lumu start blasting me with emails, I should mention they are working on expanding the features and claim that’s the reason for the current price. I don’t have any concrete evidence, but I have to assume they’re working on flash meter functionality (it only makes sense), which would make $149 a steal for a device this accurate.

What I Liked

Size. Accuracy. Simplicity. I like that the unit plugs into my iPhone, a device I’m already carrying around, and my wife likes that I’m hauling around once less piece of gear on our family vacations.

What I Didn’t Like

Until flash meter functionality comes along, I’d have to say THAT, along with the $149 price give me pause.

Final Thoughts

It makes perfect sense to integrate our smartphones with a device like this. Build a quality piece of gear, then slowly integrate additional features through software. I think the folks a Lumu are doing things right, taking their time to make sure software isn’t buggy (we experienced no issues with ours by the way) and crafting a quality piece of gear. I plan on keeping this little guy in the travel bag with my Olympus OM-D and look forward to seeing what future software updates have in store. Even if you already own a professional light meter, I think the Lumu is still a worthwhile piece of gear, especially if you’re a natural light photographer.

Tony Roslund's picture

Tony Roslund is a third-generation photographer, specializing in architecture and food imagery. He is a nationally recognized member of the American Society of Media Photographers and the Association of Independent Architectural Photographers.

Log in or register to post comments

Happy first review, Tony. Good job and thanks.

What's a light meter? Does it measure distances in light year?

Tam, trolling like a boss! Great review Tony, I am the guy that uses the back of his screen paired with the histogram. Ha

That works too, but I much prefer to start with a light meter.

I was curious when I came to kickstarter. But stopped looking at it since it was only for ambient light.

Stay tuned. I think they have something in the works.

if it comes with flash functions.. this is a buy!

I'd consider buying this at $149, but since it'd cost me €149, there's just no way.

I wonder why the exchange rates when tech is involved are always so high here in Europe?

Doesn't meter flash & $149 makes this an absolute non-starter. IF it did flash & was priced at $99, MAYBE I'd buy it. For this non-flash version, at less than $49, I'd consider it...maybe.


Thanks Tony. On the price, as a hobbyist at $149 that's maybe top heavy by $50 vs a Sekonic which (although value for money) can cost a lot more and being a software enhanced product, I like it. As the features are enhanced will likely see in-app purchase once they put the base product with flash together,. Possibly like getting 2 Sekonic models for less than the price if one?

Sounds like most people are in agreement with me that $149 may be a bit steep without flash metering. $99 seems to be the general price point most are comfortable with. Of course, as I said in the video, if they add flash metering, $149 is a deal!

You might like the SS04 sensor, it supports flash measurements and it is offered at a bargain price (

For those who might find this helpful, I'd like to point out that my company, Extrasensory Devices, makes a product called Luxi For All which is comparable to Lumu in every way except for price; while Lumu costs $150, Luxi is just $30, and it does all the same things. We don't support flash metering either, though we'd love to add it in the future if it becomes technically possible. Check us out at Thanks.

Yes, the Luxi is a nice little device for the fraction of the cost of the Lumu, but it isn't nearly as accurate. It's certainly helpful and does a good enough job for most people, but if you want Sekonic-level accuracy, especially in very low light, a dedicated pro-level sensor is going to be required.

I'd argue that at $30, the Luxi is overpriced for what it is as well.

interesting for sure, by how about Color rendering index, color temp CCT, etc...a lux meter is not enough anymore, agree? You should look at our smart spectrometer