Catch light
Catch light or catchlight is a light source that causes a specular highlight in a subject's eye in an image.[1] They are also referred to as eye lights or Obies, the latter a reference to Merle Oberon, who was frequently lit using this technique. A catch light may be an artifact of the lighting method, or have been purposely engineered to add a glint or "spark" to a subject's eye during photography. This technique is useful in both still and motion picture photography. Adding a catch light can help draw attention to the subject's eyes, which may otherwise get lost among other elements in the scene.
A catch light is not the same as the red-eye effect; in general, red-eye is an undesired effect (caused by the reflection of light from the retina inside the back of the eyeball), while catch lights are often aesthetically desirable, and produced by light reflecting from the cornea. Especially in portraiture, eyes without catch lights are often said to appear dull or lifeless. Lighting is often arranged in studio portraits specifically to create attractive catch lights.
As a specific light source, a catch light is usually fairly dim or focused, as to not affect any other part of the scene or face. Many other lighting methods, however, are known for the distinctive or unique catch light they produce. Among those methods are ring lights, which produce several highlights in a ring, and large softboxes, which produce large, square highlights.
While catchlights most often appear to be simply bright spots, as reflections of their surroundings they can contain entire images. This property is sometimes used as a plot point in movies and television. Typically in this trope (or cliché), computer magnification of a catch light is used to gain information about the surroundings of the person being photographed, essentially using the eye as a mirror.
Audiences usually perceive eyes without specular highlights to be lifeless or evil, and for this reason many cinematographers specifically eliminate catch lights on antagonistic characters.
It is also commonly found in anime, usually used in an over-dramatized manner to show different emotions accompanied by exaggerated expressions.