underexpose

Underexposure occurs when the amount of light reaching the sensor is less than what is required for a neutral exposure. The result is a darker image with reduced detail in the shadows and potential color shifts, depending on the scene and the camera's white balance.

Common causes include using too fast a shutter speed, a narrow aperture, or a too-low ISO; incorrect exposure metering in backlit or contrasty scenes; negative exposure compensation in automatic modes; or deliberately using low ambient light.

Effects include loss of shadow detail, increased noise when lifting shadows in post, reduced tonal range, and possible color cast or flat contrast. In digital images, aggressive attempts to salvage exposure can lead to visible artifacts and posterization.

Prevention involves shooting in manual mode or using exposure compensation, checking the histogram, and employing exposure bracketing in difficult lighting. Using lighting or reflectors can also help—if lighting is controlled, underexposure is less likely.

Post-processing can recover some detail but cannot fully restore erased information; adjustments to exposure, shadows, and curves, as well as white balance, may help, but pushing exposure too far increases noise and color artifacts.

Underexposure can be deliberate for mood in low-key photography and cinema, where deep shadows emphasize form and atmosphere. Such use is usually paired with careful lighting to maintain essential detail in the subject.

See also: overexposure, dynamic range.