backlighting
Backlighting occurs when there is high contrast between a light source (e.g. a window) and the observed scene.
To identify this, the backlighting method analyses first in the current frame if more than 2% of pixels are clipped (a phenomenon that occurs when a pixel sensor receives more light that it can "store", resulting in a '255' value after digital conversion for that pixel). In that case, we check if more than 60% of pixels present a luminance below '70'.
The final result of this method is a weighted combination of both the percentage of pixels at '255' and the percentage of pixels below '70'.
> A result higher than 1 indicates there might be backlighting, and with more than 11 we are quite assured of that.
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