Your iPhone is a Light Meter, Waveform Monitor, and False-Color Display with $5 Cine Meter App
Talk about your digital leatherman: The number of ridiculously handy -- and practical, and portable, all in one -- apps for filmmaking on mobile devices is probably one of the greatest tech-vantages we've got going for us these days second to low-cost high-res acquisition. Uses range from lighting plot diagramming and shooting scheduling all the way to Canon DSLR control via Android and RED control via iOS -- there's an app for all that, and more. Now, thanks to Adam Wilt of Pro Video Coalition (and a lot of other great stuff), your iPhone is now more of an asset on set than ever before -- and that's because his new $5 app Cine Meter turns your iOS device into a light meter, waveform monitor and false-color display.
There don't appear to be any videos of Cine Meter in action just yet, but Adam has included a load of technical info on his site:
See the light: Cine Meter not only gives you exposure information, it shows you at a glance how evenly your greenscreen is lit, and where high-contrast hotspots and shadows may give you trouble. With Cine Meter, you can walk around, light your set, and solve problems long before your real camera is set up, making pictures, and running down its batteries.
- The light meter shows you the stop to set as decimal readings (such as f/5.0, good for cameras with EVF iris readouts) or full stops and fractions (like f/4.0 ⅔, good for cine lenses with marked iris rings). You can calibrate Cine Meter to match other meters to a tenth of a stop, and take readings using matrix or spot metering.
- The waveform monitor shows you how light levels vary within and across a scene. They show you how even the lighting is on a greenscreen or white cove, and let you see hotspots and imbalances at a glance. The waveform’s RGB mode shows you color imbalances in the image and gives you a handy way to check for color purity on a greenscreen or bluescreen.
- The false-color picture lets you define allowable contrast ranges, and see instantly which shadows are underexposed and what highlights risk clipping:
Limitations of Functionality:
Here's Adam with additional details on how the app works, which is contingent on the ways iOS does or does not allow apps to use to use onboard cameras:
Cine Meter can only do what an iDevice (iPhone / iPad / iPod touch) lets apps do: lock and unlock exposure and white balance, but not preset either one to a known value; and read out scene brightness values. These limitations define what Cine Meter can -- and can’t -- do.
- The light meter is absolute -- you can count on its readings to mean what they say, regardless of circumstance, since they’re calculated from the camera’s reported brightness value. Once you calibrate Cine Meter to your reference standard, it should always give you correct readings.
- However, the picture, false-color picture, and waveform monitor displays are only relative—they show scene brightness values relative to other levels in the scene, but the levels of those images and waveforms depend on how the camera sets its exposure, which often differs from the brightness value the camera reports to the light meter, as described in How It Works.
- For this reason, you can’t directly compare light meter readings with waveform or false-color levels!
- You can’t preset an exposure level or a white balance and then use the displays to show you absolute levels. iPhone / iPad / iPod touch cameras don’t let you manually preset values; they only let you lock in the current auto-exposure or auto-white-balance setting, so you can’t set the scopes for, say, ISO 800 @ 1/48 sec @ f/4.0 with a color temperature of 3200K.
- The only way to set a particular exposure level is to trick the camera by showing it the “correct” light (for example, using a gray card) and then locking its settings. Once locked, you can then look at the pictorial displays to see how tones and colors in a scene render relative to the locked settings.
That’s the key to getting the most out of Cine Meter: treat it like a point-and-shoot camera with exposure and white-balance locks (which is really what it is, only with fancier readouts), and you’ll be able to “fool” it into doing what you need.
This is a lot like the way you used to have to fool older Nikon DSLRs into the desired exposure for shooting video, but much more understandable here -- it's only a phone (or pad, or pod) after all. That said, this app seems to put practical functionality into your iPhone that's a heck of a lot more practical than, say, trying to shoot a film on one. It's not going to be perfect, and shouldn't outright replace a dedicated professional light meter -- or the waveform readout you would get from your A camera in proper placement, for that matter -- but it's a heck of a start. As such, it's a tradeoff, but one in which you get serious value out of $5, a bonus when compared to the tag attached to pro meters (or waveform monitors!). I can see a lot of qualitative mileage out of this little bag of tricks in the right hands -- which, of course, are your hands given skillful usage.
You can check out Adam's site for the full details -- an Android version is coming, by the way.
In the meantime, what are you iOS users waiting for -- I can't try it out for myself (yet, at least), so let us know about your experiences with Cine Meter in the comments below!