Metering

The meter reads the amount of light illuminating the subject, not light reflected from the subject, so the meter ignores the subject and background characteristics.On the first picture everything it's black and on the second picture it's super white,why? because we use light metering to create these to diferents photos. They are useful when there is a relatively small object within your scene which you either need to be perfectly exposed, or know that it will provide the closest match to middle gray.