Just a quick example between using AE Average, or AE Spot, and when to use them.
First, the scene. The first image is shot at 24 mm and I have used AE Average. This, or AE Multi, would be the normal metering mode for these types of scenes. My preference is AE Average.
(Note : I have lightened this first image. the others are exactly as shot)
Now, if I zoom in to 720 mm, on the flowers just left of the central figures head, and still use AE Average, the result is that the flowers 'blow out'.
Why ? This is because the AE meter is still trying to 'average' the scene. It is ignoring the highly lit area and trying to 'equalise' the exposure. This is not a fault of the camera, it is operator error. The camera is only doing what we have set it to do.
So, what to do ? If we set the camera to AE Spot, then it will expose for the centre of the scene. In this case, the flowers. A far more pleasing outcome.
Using AE Spot, particularly when using long focal lengths, will give a far better result. It is a good idea to also use AF Center so that our focus point is at the centre of the image.