A few months ago, I posed a question on the Cinematographer’s Mailing List (CML). A lightmeter had been released with a flat panel display, making the device closely resemble a smartphone with a lightmeter sensor stuck on top. Would it be possible to turn an iPhone into a lightmeter, utilizing the built-in camera as the sensor? How about making it a color meter? There was much fanciful back-and-forth discussion, and noted engineer Adam Wilt outlined the difficulties posed, especially in mapping and controlling the internal camera and its automatic adjustment programming. There was already a basic iPhone lightmeter app available, but it was only accurate in midtones with very limited controls.
Adam became intrigued, and recently he debuted the Cine Meter app, which will work on most Apple portable iData devices (iPhone 3GS & up; iPod touch 4 & up; iPad 2 & up, iPad mini). Alas, the color meter was impossible, as there were too many differences between the various devices, and there was no way to be sure of the accuracy of the color spectrum mapping. But there was a lot more Adam was able to pack in.
Cine Meter is more than a simple exposure meter. A standard reflective lightmeter will view light of a particular angle and average it to a single brightness reading. For more precise measure, a spot meter is a reflective meter of a very narrow angle of view, but it still only averages the overall brightness of that imaging area. Cine Meter reads the reflective brightness in a wide or narrow (spot) range, but then it breaks the data out into far more information. A false color mode shows the range of exposure throughout the image.
Another way this data is expressed is in a waveform monitor. Yes, this $4.99 app is actually a detailed waveform monitor, a device usually costing several thousand dollars. The waveform can show exposure levels across the image in a vertical percentage scale. It can also be set to split the red, green and blue color channels and show their respective levels on the waveform. This allows you to gauge if part of an image may begin to clip or fall below minimum desired exposure level. It is excellent for judging the evenness of illumination across a green screen, or comparing relative exposure levels of two areas within a frame.
I can definitely see Cine Meter being useful on set as a portable waveform monitor, a lighting tool when the production camera is unavailable or impractical to utilize, and as a location scouting tool. Certainly it is useful wherever one may otherwise wish to use a traditional reflective light meter. For just a few dollars, I cannot imagine why any Cinematographer, DIT or Gaffer would not have this in his or her pocket.
Adam is currently developing an Android version of Cine Meter, but for now you can download it from the iTunes store.