Calculating EV and then Lx is pretty simple. The problem starts when trying to calculate these by using EXIF data that come from different cameras.
I tried capturing a static object in the exact same position, angle and light condition, with 2 different cameras, and the EV result was completely different.
The thing is, I’m not sure how to treat the various parameters which I believe have dramatic influence on the light value, e.g. focal length. In all equations that I found on the internet, the only parameters specified were Aperture, Exposure and ISO.
Does anyone know how to handle this situation?