Light measuring in android?

Question

I’m trying to get a uniformed value that indicates a light level from the Android back (main) camera. I’m using several Android devices and the object captured is absolutely static (same object in the same light condition, in the same angle and the same position) and I get deferent value results. My calculation is based on `Aperture`, `ISO`, `exposure time` and `exposure compensation`. I tried to do: EV = AV + TV = log(Aperture^2,2) + log(1/exposure_time,2). I also tried some other methods from the following article: http://dougkerr.net/pumpkin/articles/APEX.pdf Anyhow… the results I get differ from device to device… Does anyone know how to solve it? Maybe there are more values that I’m ignoring? Thanks.

Answer 1

Cameras vary in how and where they measure the amount of light on the subject. Most are adjustable with various settings. I've found that almost every phone/camera is slightly different and if you're serious about the results you get, you'll need to determine how your specific camera handles light.

Many photo apps measure the average light on the entire image. Some narrow that down, even to one specific spot such as an individual face in a crowd of faces. The way light is measured is adjustable in virtually all phone/cameras.

The get the "correct" reading, zoom into the one specific spot you want as the mid-range. Or, if you (and the camera) are in the same light as the subject, hold the palm of your hand in the light in front of the lens. That's your mid-range light, a 5 on a scale of 1 to 10. Like lightly browned toast, neither light nor dark.

Lock that f-stop and shoot away.