Metering Calculator — Exposure Compensation

Camera meters assume the scene averages to 18% middle grey. Snow is much brighter than middle grey, so the meter reduces exposure to bring it back to grey — resulting in underexposed, dingy-looking snow. Add +1 to +2 stops of exposure compensation to render snow as white.

Use spot metering when your subject is significantly brighter or darker than the background, such as a performer on a dark stage, a backlit portrait, or a bird against a bright sky. Spot metering reads only 2-5% of the frame, letting you meter precisely on your subject.

All camera meters are calibrated to expose the scene as 18% grey (middle grey). This works for average scenes but fails for predominantly bright or dark subjects. Understanding this lets you predict when exposure compensation is needed.

Adjust ISO if you want to keep aperture and shutter speed fixed (e.g. for consistent depth of field and motion blur). Adjust shutter speed if depth of field is more important. Adjust aperture if shutter speed must stay fixed (e.g. for motion blur control).