by BD Mitchell
One hundred facts that are interesting but ultimately useless.
The Red-Eye Effect
- physiology -
The "red-eye effect" is a phenomenon associated with flash photography. A camera flash occurs too fast for a human pupil to react, allowing much of the light to pass through the iris and reflect off the back of the eye. If the camera lens is placed too close to the camera flash, the light reflects directly back to the camera and is captured on the photograph. The red coloration is caused by a dense concentration of blood vessels at the back of the eye.
The intensity of the phenomenon varies with the amount of melanin (a light-absorbing pigment) behind the retina. Resultantly, red-eye is more prominent in people with lighter skin and lighter eye color due to a genetic lack of melanin.