Average flash metering is pretty straight-forward. All the camera has to do is measure all the flash sensor points, add them up and then average the total. Nothing fancy. That means that all points get equal treatment whether the point is on a background area or the main subject.
Evaluative is a lot more complicated. The camera has to determine where the subject is first (ETTL-II) or where the AF point is (ETTL) and then bias the flash metering for the subject or the AF point using a complex set of algorithms to determine the final flash exposure.
0 Comments