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Lumu turns iPhone into incident light meter


Are light meters outdated? Lumu doesn't think so and neither do its supporters, whose pledges more than doubled the Kickstarter project's goal on the first day. In fact, it took less than five hours for the company to raise its minimum start-up target of $20,000.  

This tiny device, which reads the light via a sphere about the diameter of a quarter, is an incidenct light meter. As such, it reads the light falling on the subject rather than the light reflected off the subject, which generally gives a more accurate reading (digital cameras use a reflective light meter). The meter plugs into the iPhone's headphone jack, so no batteries are needed, although we have to wonder how much power it demands from the iPhone's battery. Suggested exposure settings are shown on the meter's app and can be saved to the cloud, along with other data, for future reference. Otherwise, just set the exposure on your camera (digital or film) and you're good to go.

Lumu has also designed a leather case and a neckstrap for carrying the light meter when you're out shooting. While different packages are available on Lumu's Kickstarter page, pledge a minimum of $99 now for a $50 discount and free, worldwide shipping. The Lumu is expected to ship this October with an estimated retail price of $149. 

It's a very cool idea and one that, from its fast and furious Kickstarter support, seems to fill a need for an ultra-portable, easy-to-use light meter. Since the Lumu works only with natural and continuous light sources (and not flash), we imagine that the Lumu's convenient size and portability would be its main selling points. Even though there are more sophisticated professional light meters on the market (which are usually more expensive), the Lumu team's enthusiasm and attention to detail holds promise for this diminutive iPhone accessory. 

(For a comparison, see our story on another iPhone light meter, the Luxi.)

The tiny Lumu fits neatly into the iPhone's headphone jack and needs no batteries.
A leather carrying case and neckstrap make it convenient to bring the Lumu wherever you go.


Total comments: 14

For those of you wondering why you would need an incident light meter; in difficult natural light situations it tells you how much light is actually falling on the subject which in turn lets you capture the relative light values in the setting as your eye sees it. We have more than 150 years of experience and science to call on for using incident meters.
By contrast modern matrix reflected meters in cameras do a great job for most things, but they are prone to failure if there's a lot of white or black within the frame. 95 percent of the time your camera will do pretty well, but in that 5 percent incident meters they can be a lifesaver.
Plus using a light meter is way cooler than chimping.

Model Mike

Could be a cool device if you shoot with film, but totally inappropriate for digital since subject reflectance is critical to avoiding saturated highlights.

Comment edited 2 times, last edit 2 minutes after posting
ian adams

This sounds like a solution in search of a problem. The built-in
exposure meters on dSLR and point-&-shoot digital cameras are superb, and together with in-camera histograms provide precise exposure control. The current iPhone 5 also has a good exposure meter and does not allow you to set an exposure manually from a meter reading. Finally, incident light meters may be useful in studio photography but they are generally useless for scenic and other outdoor photography.

The Lumu is nothing more than an expensive gimmick.


Ever heard of a magic device called a film camera?


For the love of Photography, stop creating non-sense accessories. Just bring a decent P&S camera and keep your iPhone for phone calls and texting.

1 upvote

Here's a better use for an iPhone.


Maybe I'm missing something here but what's the point of measuring the incident light falling on the Lumu sphere instead of the light reflected off subjects we want to capture? I mean, it is the light that is reflected off the subjects that hits the sensor. And how can the Lumu app suggests the right exposure if it doesn't know the level of reflectance of the subjects?


You are missing the point of incident light meters in general. Reflective light meters like the one in your camera want your subject to be as bright as 18% gray, always. This works well for Caucasian skin most of the time, but if you point your camera at a dark or light subject, the resulting exposure will probably be over or under. An incident light meter meters for the ambient light, so your subject will look more like it does in real life, which often enough is not the same as 18% gray. Also, if your subject is against a dark or bright background, a reflective meter will get it wrong unless you take spot readings for each shot. Learn to shoot manually and to be your own judge of exposure and you will realize just how often even the best in-camera meters get it wrong.

Comment edited 10 minutes after posting

Part way down, it describes reflective vs incident meters.

As everyone is getting rid of their incident meters, I pick them up for cheap. I got a couple of Gossen Lunasix F meters I play around with.


Comment edited 1 minute after posting
1 upvote

@JackM: I understand why incident light meters were useful back when cameras didn't have spot metering, but most modern cameras now have that feature so I just don't see the point.
You mentioned Caucasian skin vs darker skin requiring different exposures. That is one of the scenarios where the Lumu is pointless, it doesn't know the nature of the subject and just suggests exposure based off available light (that's how it works, right?)

Comment edited 3 minutes after posting

No. Spot metering reads reflected light and camera tries to compensate to what the camera understands as average. Spot metering a white person will most probably underexpose the image by 1 stop. Spot metering for a black person will overexpose the picture by 1 stop. Incident meter will always be correct because it will read the light falling on the subject, i.e. the correct amount of light illuminating the scene/object of interest.


@BBViet: You've got it the other way around. A reflective light meter doesn't know the nature of the subject, but it needs to. It sees a black door and it wants to paint it gray. That is where the photographer steps in and applies exposure compensation. An incident light meter does not need to know the nature of the subject. It will give you a reading that makes the subject look as it did while bathed in the light available.

Comment edited 1 minute after posting

I still have my trusty Minolta Meter V. As Tremint said, no strobe metering feature on the iPhone meter.... Cool idea, but I'll stick with the my classic.

1 upvote

It does not measure flash/strobes. Thats the real use of light meters now a days. I dont see an input to trigger the strobes. Will wait for version 2.0

1 upvote
Total comments: 14
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