Red-eye Removal
A process that detects and corrects the red-eye effect caused by flash photography, restoring natural pupil color.
Red-eye removal corrects the phenomenon where pupils appear bright red in flash photographs. Red-eye occurs when a flash fires in dim conditions while pupils are dilated, causing light to reflect off the blood vessels in the retina back into the camera lens.
The correction process detects red-colored pupil regions in the image and reduces the red channel in those areas, replacing it with black or dark brown tones. Most camera apps and smartphones include automatic red-eye correction that processes images immediately after capture.
Prevention techniques include using the camera's red-eye reduction mode (which fires a pre-flash to constrict pupils) or having subjects look at a bright area before shooting. Pets may exhibit green or yellow eye glow from the same principle. As a form of color correction, red-eye removal typically uses a mask to selectively modify only the pupil area.