home cinema A home cinema, also called home theater, is a home entertainment audio-visual system that seeks to reproduce a movie theater experience and mood using consumer grade electronic video and audio equipment and is set up in a private home. In ...

and

video editing Video editing is the post-production and arrangement of video shots. To showcase excellent video editing to the public, video editors must be reasonable and ensure they have a thorough understanding of film, television, and other sorts of videog ...

technology, bias lighting is a weak

light source Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

on the backside of a screen or monitor that illuminates the wall or surface behind and just around the display.

Motivation

The purpose of bias lighting is to reduce the perceived brightness of the display as a result of the contrast with the slightly illuminated area around it. This reduces the

eye strain Eye strain, also medically termed as asthenopia (), is a common eye condition characterized by nonspecific symptom, non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional diplopia, double vis ...

and fatigue that occurs when viewing a bright display against a very dark background for an extended time, and increases the perceived blackness, perceived highlights, and overall contrast of the display.

History

Bias lighting has been used since the early days of television in the form of "TV lamps", often taking the shape of an animal, that were set atop television sets and projected light onto the wall behind the set. In 2002, Philips Consumer Electronics developed and patented a lighting system that allowed the background illumination to follow the brightness and color of the TV image. In addition to reducing the brightness-contrast of the image with the background, this also extended the image across the wall, making it appear larger. This system was integrated into a flat TV and introduced to the market in 2004 under the name “Ambilight”. As of the 2000s, bias lights often use

LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...

s, attach to the backside of

flat-panel displays A flat-panel display (FPD) is an electronic display used to display visual content such as text or images. It is present in consumer, medical, transportation, and industrial equipment. Flat-panel displays are thin, lightweight, provide better ...

, and draw power from a

USB Universal Serial Bus (USB) is an industry standard, developed by USB Implementers Forum (USB-IF), for digital data transmission and power delivery between many types of electronics. It specifies the architecture, in particular the physical ...

port. Some bias lighting kits even use a webcam pointed at a TV or monitor screen to read colors and change television backlights accordingly.

Color temperature

Bias lights with a

color temperature Color temperature is a parameter describing the color of a visible light source by comparing it to the color of light emitted by an idealized opaque, non-reflective body. The temperature of the ideal emitter that matches the color most clos ...

of 6,500 K match the temperature of most monitors' white color, which is derived from the

CIE standard illuminant D65 A standard illuminant is a theoretical source of visible light with a spectral power distribution that is published. Standard illuminants provide a basis for comparing images or colors recorded under different lighting. CIE illuminants The Inte ...

. They are used in professional editing environments and are recommended to maximize the fidelity of the perceived image. In home cinema, bias lighting that is no brighter than 10% of the display's brightest spot and with a

color rendering index A color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with a natural or standard light source. ''Color rendering'', as defined by the Internat ...

of at least 90 is recommended. There is some debate about the proper brightness levels of bias lighting for HDR content, with SMPTE recommending 4.5 nits and the Imaging Science Foundation recommending 10%, but sometimes as high as 15%.

References

{{reflist Film and video technology Lighting

Motivation

History

Color temperature

See also

References