LED light used in photography
General-purpose lighting needs white light. LEDs emit light in a very narrow band of wavelengths, emitting light of a color characteristic of the energy bandgap of the semiconductor material used to make the LED. To emit white light from LEDs requires either mixing light from LEDs of various colors, or using a phosphor to convert some of the light to other colors.
The two simplest methods of producing white light LEDs are RGB or phosphor. RGB or trichromatic white LEDs uses multiple LED chips emitting red, green, and blue wavelengths. These outputs combine to produce white light. The color rendering index(CRI) is poor, typically 25 - 65, due to the narrow range of wavelengths emitted.
The second basic method uses LEDs in conjunction with a phosphor to produce complementary colors from a single LED. The most common method is to combine a blue LED with a yellow phosphor, producing a narrow range of blue wavelengths and a broad band of "yellow" wavelengths actually covering the spectrum from green to red. The CRI value can range from less than 70 to over 90, although a wide range of commercial LEDs of this type have a color rendering index around 82.
The colors available from both the basic types of white light LED is adjustable to a certain extent, with color temperatures in the range of 2,200 K (matching incandescent lamps) up to 7,000 K are widely available.Higher CRI values can be obtained using more than three LED colors to cover a greater range of wavelengths. Tunable lighting systems employ banks of colored LEDs that can be individually controlled, either using separate banks of each color, or multi-chip LEDs with the colors combined and controlled at the chip level.
A significant difference from other light sources is that the light is more directional, i.e., emitted as a narrower beam. LED lamps are used for both general and special-purpose lighting. Where colored light is needed, LEDs that inherently emit light of a single color require no energy-absorbing filters.
BAPS Shri Swaminarayan Mandir Atlanta Illumination with color mixing LED fixtures
Computer-led LED lighting allows enhancement of unique qualities of paintings in the National Museumin Warsaw
White-light LED lamps have longer life expectancy and higher efficiency (more light for the same electricity) than most other lighting when used at the proper temperature. LED sources are compact, which gives flexibility in designing lighting fixtures and good control over the distribution of light with small reflectors or lenses. Because of the small size of LEDs, control of the spatial distribution of illumination is extremely flexible,and the light output and spatial distribution of an LED array can be controlled with no efficiency loss
LEDs using the color-mixing principle can emit a wide range of colors by changing the proportions of light generated in each primary color. This allows full color mixing in lamps with LEDs of different colors.Unlike other lighting technologies, LED emission tends to be directional (or at least lambertian), which can be either advantageous or disadvantageous, depending on requirements. For applications where non-directional light is required, either a diffuser is used, or multiple individual LED emitters are used to emit in different directions.
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