Pros & Cons
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- Compact.
- Measures light and color.
- Very accurate.
- Less expensive than dedicated meters with similar capabilities.
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- Requires iOS device to work.
- Lightning port might not be around forever.
We liked the first Lumu light meter. The Kicktarter success story—funded and delivered to backers as promised—was a compact incident light meter that used your smartphone's processing power and an app to take readings. When we reviewed it in early 2014 we couldn't predict that its seemingly eternal interface—the 3.5mm headphone jack—would disappear from phones so quickly. The new Lumu Power ($299) uses Lightning to connect to an iPhone (there's no Android version), and adds a lot of functionality you didn't get with the original Lumu. It costs more, but it also does more.
Design and Features
The new Lumu Power is similar in design to its predecessor. It's a small hemisphere with a flat back and a lone data connector—in this case, Lightning. Its diameter is about the size of a quarter, and a small black carrying case is included.
You'll need an iOS device with a Lightning connector and iOS 8 (or newer) installed. I tested the Power with both an iPhone 6 Plus and 8 Plus. It's easy enough to get started; just plug it into the phone and iOS prompts you to give it permission to use. If you grant it, the Lumu app opens automatically.
The app shows you everything the Lumu can do. It can measure Illuminance (in Lux), take ambient or spot light readings (the latter using your phone's camera rather than the meter), work as a flash meter, and measure both color temperature and chromaticity.
The interface sets the Lumu apart from handheld meters. If you've used a light meter you know that they're not always intuitive devices. Instead of a small LCD, the app show information in large type, and the touch interface takes the guesswork out of what button does what.
Light measuring uses the domed side. To take an ambient reading you'll want to position the meter directly in front of the subject of your image, with the dome facing toward the camera lens. Photographers can use the Photo Ambient module to see the proper aperture, shutter speed, and ISO needed to get a good exposure.
You can change any one of these components and the others will adjust automatically. The meter also gives you the ability to take a reading to intentionally underexpose or overexpose a shot, and can adjust its output to compensate for any ND filters you may be using. There are also tools to calculate values for multiple exposure images and pinhole images.
The Cine/Video module is quite similar, with the same options for exposure compensation and ND. It adds frame rate, an essential component for cinematography.
For both video and imaging, I found the Lumu to deliver deadly accurate results. I dialed in its suggested exposure settings into a digital camera and netted properly exposed stills and video. This was done in a tricky exposure setting, with a white backdrop that tends to cause in-camera meters to underexpose by a third to two thirds of a stop.
Flash metering is new to the Lumu Power—it wasn't included with the original when we reviewed it. When this module is active it measures the exposure you'll want to use with studio strobes, and also shows duration of the flash output in a graph. We found that our group of studio strobes fired for 1/297-second. Dedicated meters with flash measurement capability start selling for around $200, a bit less than the Lumu Power.
Color measurements are another new addition. I used the meter to measure the temperature of the LED lights we use in our studio testing scene to confirm a suspicion I had for some time—they are not truly 5600K as advertised, but actually a little warmer than daylight, 4470K, with a slight magenta cast. If you're using lights that output different temperatures the app includes a tool that lets you know which filters to use to balance them.
Finally there's Chromaticity. This measures the actual hue of colors and maps it on a graph. This isn't a tool I need for photography, but if you need it for you work, you'll be happy to know that it's there.
It's in the color measurement function that the Lumu shows up as a value proposition. The least expensive color meter I could find, the Kenko KCM-3100, sells for $800.
Conclusions
The Lumu Power is a strong follow-up to the original meter. It is just as accurate and useful when it comes to measuring light, but swaps out the now dated 3.5mm connector for a Lightning port. It's accurate, compact, and a fine tool for measuring the intensity and color of light. We have no hesitation recommending it on functionality alone—it's a modern meter and its app-based interface is easier to use and more intuitive than the buttons used to control standalone meters.
There is one caveat. Lumu itself has been around as a company for a few years, but there's no guarantee that it will update its app forever, and as much as Apple has invested in the Lightning connector, we don't know if it'll remain the standard for iOS devices in years to come. There's a chance that, at some point in the future, you'll have an excellent light meter, without a modern device with which to pair it. If the Lumu app stops getting updates, or if Apple ditches Lightning, you'll need to an old device around to keep running it.