Red-eye Effect

The red-eye effect in photography is the common appearance of red pupils in color photographs of eyes. It occurs when using a photographic flash very close to the camera lens (as with most compact cameras), in ambient low light. The effect appears in the eyes of humans and animals that have tapetum lucidum.

Theatrical followspot operators, positioned nearly coincidentally with a very bright light and somewhat distant from the actors, occasionally witness red-eye in actors on stage. The effect is not visible to the rest of the audience because it is reliant on the very small angle between the followspot operator and the light.

The feature film Blade Runner intentionally induced a red-eye effect to indicate that certain characters were "replicants," an artificial life-form in the story. The effect relied on a semi-silvered mirror directing light at the actors on the same incidence as the camera.