Originally Posted by homey
That means that only centre weighted exposure is working!
No, it behaves very differently. I tested all this in a semi-dark room with a bright TV in it. In this way I can easily see how changing the metering mode affects the image by moving the phone to shift the position of the TV set around the image.
For instance, in spot metering mode this quickly enabled me to determine that, if I put the TV screen to one side of the frame and tapped on the screen to shift the focus point, the exposure was still set by the brightness at the centre of the phone screen i.e. it didn't move with the focus point.
Similarly, by cycling through all three metering modes (centre-weighted, spot and matrix), I could see that if I was in centre-weighted mode, the exposure changed very little, regardless of where the TV screen was in the frame. Conversely, in spot metering mode, if I put the TV in the centre of the frame, the camera changed exposure to make the TV screen perfectly exposed (and the room very dark). But if I moved the camera so that the TV screen was even just slightly outside the centre focus box, the exposure immediately changed to expose the room correctly (leaving the TV screen way too bright).
I've tracked down a very comprehensive S3 camera guide which confirms what I have found. it says "Spot metering measures the brightness only at one spot, which is the middle in this case and it ignores everything else within the frame".
You can read it here:
The Galaxy S3 Gallery: [Guide] Samsung Galaxy S3 Camera Usage Guide, Part 1: Hardware and Feature
And here is a quick photographers' guide to the three metering modes to explain how they differ in the way they measure exposure: