White is a color (although some describe it as an achromatic colour, or an absence of colour) that has high brightness but zero hue. The impression of white light can be created by mixing (via a process called "additive mixing") appropriate intensities of the primary colour spectrum: red, green and blue, but it must be noted that the illumination provided by this technique has significant differences from that produced by incandescence (see below). (?add comment about color gamut of RGB vs incandescence illumination here? or rework?)
|Table of contents|
2 White Light
3 Standard Whites
5 Usage, symbolism, colloquial expressions
6 People Whose Surname Is White
Until Newton's work became accepted, most scientists believed that white was the fundamental color of light; and that other colors were formed only by adding something to light. Newton demonstrated that White was formed by combining the other colors.
In the science of lighting, there is a continuum of colours of light that can be called "white". One set of colours that deserve this description are the colours emitted, via the process called incandescence, by a black body at various relatively-high temperatures. For example, the colour of a black body at a temperature of 2848 kelvins matches that produced by domestic incandescent light bulbs. It is said that "the color temperature of such a light bulb is 2848 K". The white light used in theatre illumination has a colour temperature of about 3200 K. Daylight has a nominal colour temperature of 5400 K (called equal energy white), but can vary from a cool red up to a bluish 25,000 K. Not all black body radiation can be considered white light: the background radiation of the universe, to name an extreme example, is only a few kelvins and is quite invisible.
Standard whites are often defined with reference to the International Commission on Illumination's (CIE's) chromaticity diagram. These are the D series of standard illuminants. Illuminant D65, originally corresponding to a colour temperature of 6,500 K, is taken to represent standard daylight.
Computer displays often have a colour temperature control, allowing the user to select the colour temperature (usually from a small set of fixed values) of the light emitted when the computer produces the electrical signal corresponding to "white".
Usage, symbolism, colloquial expressions