Manual exposure adjustment against meter reading — corrects for scenes the camera underestimates or overexposes. Essential for backlight, snow, or dark subjects.
Your camera's light meter measures grayscale tones — not what you want to see. If the scene is predominantly white (snow, a light shirt against a dark background), the meter adjusts downwards, making the shot dark. Conversely, if your subject is in front of a black background, it will be overexposed. This is where exposure compensation comes in — the manual correction of exposure relative to the internal measurement. It's not an absolute value, but a delta: +1 EV (Exposure Value) means one stop brighter than the meter suggests. The concept exists in practically every modern camera — Sony, Canon, RED, even smartphone apps have it.
In practice, this works on set like this: Test the scene, look at the histogram or on the monitor. If the important areas (face, eyes) are too dark, set +0.5 to +1.5 EV — depending on how dark the background is. Backlit scenes often require +1 to +2 EV so the face doesn't become a silhouette. Classic mistake: beginners compensate in the wrong direction or over-compensate. A stop difference is clearly visible, not subtle. Work in 0.5 increments, not whole stops.
Important: Exposure compensation only works when you are operating in automatic or semi-automatic mode (aperture or shutter priority). In manual mode M, you simply adjust the aperture or shutter speed directly — that is then true manual exposure, no longer compensation. With digital cameras, it's cleaner to underexpose slightly in the raw footage (Log curves, RAW) and recover it in post, rather than over-compensating in-camera and blowing out details. This saves you noise and gives the colorist more room to maneuver.
Specifics with different metering modes: In spot mode (center-weighted or zone metering), your compensation directly affects the measured area. In matrix or evaluative mode (all-over), compensation can seem imprecise because the camera has already tried to balance multiple scene areas. Therefore, many cinematographers prefer to meter manually or use external light meters for critical scenes. The compensation control is a tool for fast-paced sets — nothing more, nothing less.