spinworkxroy said:
Eh, maybe i rephrase my question.
For example, when using zone AF..if for example i use center-weighted metering, but i move the zone to the bottom most left corner (for a landscape shot for example), does the camera do the metering from the CENTER of the screen or does it do metering on the zone at the bottom most left that i moved the AF to?
I'm asking because for example, i'm doing an AF on a rock on the bottom left and i want the exposure to be based on that rock rather than the middle of the frame…or do i have to do an AE lock on the rock, and then reframe the shot?
Center-weighted is
center weighted, regardless of the AF point/zone you select.
When using any metering mode other than evaluative, if you want to meter on a specific part of the scene, you must do just that - set to spot metering mode, put the spot metering circle where you want to meter, press AE lock, then recompose and take the shot. Evaluative biases the metering toward the selected AF point, but still averages the entire scene (and compared it to the database of stored image parameters).
This diagram shows how the metering is weighted (the coverages are from the 7D; the 5DIII is 6.2% for partial and 1.5% for spot - see p. 167 of the 5DIII manual.
Only evaluative is linked to the AF point. On 1-series bodies, spot metering can also be linked to the AF point (or iteratively sampled from up to 8 points in the scene then averaged, called multi-spot metering).