How each metering system works
Discover which parts of the image each mode takes into account
3d matrix metering
This mode measures the light from hundreds (or even thousands) of points across the entire image area. It then uses other information such as the colour and focusing distance to calculate the ‘best’ exposure.
Here, the camera measures the brightness of the whole image, but takes around 75% of the reading from a circle in the middle of the frame. This circle is typically around 8mm wide, but on models like the D7000 you can alter its size.
Spot metering measures from a small area instead of across a large area of the frame. The size is roughly equivalent to the size of the focus point bracket, and corresponds to the active focus point when using single-point AF.