Light sources incandescent tungsten-filament

Clearly, standardized light sources are desirable for color matching, particularly in view of the phenomenon of illuminant metamerism described below. Over the years CIE has defined several standard illuminants, some of which can be closely approximated by practical sources. In 1931 there was Source A, defined as a tungsten filament incandescent lamp at a color temperature of 2854 K. Sources B and C used filtering of A to simulate noon sunlight and north sky daylight, respectively. Subsequently a series of D illuminants was estabUshed to better represent natural daylight. Of these the most important is Illuminant E). ... 

Real or gray bodies deviate from these ideal blackbody values by the A-dependent emissivity, but the color sequence remains essentially the same. This mechanism explains the color of incandescent light sources such as flames in a candle, tungsten filament light bulb, flash bulb, carbon arc, limelight, lightning in part, and the incandescent part of pyrotechnics (qv). 

Two light sources are commonly used in this spectral domain. An incandescent lamp made from a tungsten filament housed in a glass envelope is used for the Visible... 

Tungsten filaments are the light source in incandescent light bulbs. The efficiency of such a bulb increases dramatically with increasing temperature, because of the shift in A.max. Figure 5.3 illustrates this efficiency using a historical (but intuitive) unit of brightness—the candle. 

Quartz-iodine lamp A tungsten filament high-intensity incandescent lamp which contains iodine in a quartz envelope. Used primarily as a source of visible light. 

Incandescent lamps are the simplest type of light source. They usually consist of a heated rod or filament of tungsten in an inert gas such as nitrogen or argon at a pressure of approximately 1 atm. 

The working temperature of tungsten-filament incandescent lamps lies between 2200 and 3000 K. Therefore, they emit light mostly in the visible and infrared parts of the spectrum. Such a source of radiation may be useful in photoreactions of coloured chromophores, for example in the photodissociation of bromine or chlorine molecules to initiate photohalogenation reactions (Section 6.6.1). 

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