3D Colour Matrix, Center Weighted & Spot Metering. What they are for and in which situations to use them.
Also regarding exposure compensation it states in the Nikon manual:
"Only the exposure information shown in the electronic analog exposure display is affected, shutter speed and aperture do not change"
...when clearly in the viewfinder illustrations the shutter speed and aperture are affected, they are also in the top screen of my D90. This is confusing me because at first I didn't think exposure had any link with shutter speed or aperture as when using live view you can change the exposure and see the difference, but when you actually take the shots higher exposure setting will use longer shutter speeds, and lower the opposite.
Is the live view dimming when lowering exposure just a preview of what the end photo will look like? So technically Nikon could also make it so that you can preview the results of longer shutter speeds in terms of brightness (by increasing the amount of light in the LCD)?
Basically the camera uses each of it's "zones" (Nikon has about 500 compared to Canon's 30 or Pentax's 77). It then determines the amount of light each zone is giving off or requires. When you do the "Color Matrix Metering" it evaluates every zone and averages them together to create an "even" image. This is probably useful for landscapes or city-scapes where you want every part as evenly exposed as possible.
Center weighted is the same, except there is a slight emphasis on the center portion of the image.
Spot weighted is the VERY VERY center (about 1% of the frame) is metered. This works well with portraits where you want the center of the image to "POP" out and have the background under exposed, however, spot metering doesn't work with certain focusing screens.
Samsung GX-10, , SA 18-55mm
Canon 5D Mark II, 40D, EF 17-40mm f/4 L, EF 24-105mm L IS, EF 50mm f/1.4