"Red-Eye" Phenomenon

Definition:

A phenomenon where the people or animals in eye-dominant photography appear to have red eyes due to the reflected flash illumination

Description:

The strong light emitted from a flash is reflected from the retina of the eye where the blood vessels are concentrated.  This reflected light is sensed by the film and the eyes of the subject appear red on the printed picture.  The chance of this occurring differs from person to person, but it generally occurs more with people with light colored eyes (blue and green). 

The occurrence of the "Red-Eye" phenomenon can be reduced by:

"    Taking pictures in bright surroundings (subject's pupils contract)

"    Asking the subject to face the camera

"    Moving as close to the subject as possible

"    Using an external flash

Some cameras developed recently have functions to reduce the occurrence of the "Red-Eye" phenomenon by means of a pre-flash or pre-light emission.