They all say and teach the rule that camera exposes to 18% grey. Then they go and show an example of shooting a white board or black board and they both show as a grey board in the camera. Great, but how does the algorithm actually work for a normal scene?
Does it try to find the brightest spot in the scene and make that 18% grey? Does it find an middle grey spot and then make that 18%? Does it do some kind of weighting from different areas of the frame? If so, does it all average out to be 18% grey after the weighting?
And how does the algorithm changes from matrix to spot? Does spot make the center pixel 18% grey and that's it?
I know that each brand have a slightly different algorithm but I'm asking for the general theory and not worrying about specific optimizations.
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