Whenever your camera isn’t in full manual mode, it measures the amount of light reflected from the scene (a process called ‘metering’) and uses inbuilt algorithms to decide how to set the aperture, shutter speed and/or ISO. The camera doesn’t understand what exactly you are trying to capture, so by default chooses exposure settings that result in the tones in the image averaging to a mid-grey tone. Adjusting the metering mode changes which parts of the image frame the camera …