Daylight

Daylight is the - visible - light from the sun (sunlight), or the sunshine, which can be seen from sunrise to sunset, so the natural light of the clear day.

Description

The light of upstanding sun that hits the earth's atmosphere by the earth's surface, can be adjust by light with a color temperature of about 5777 Kelvin ( a reference value for the color of the sun ), but has a more complex light spectrum. In the CIE standard colorimetric some standard light types of class D ( Daylight ) are defined as the standard lighting, D50 (5000 K), D55 (5500 K), D65 ( 6500 K), D75 ( 7500 K) D9300 - as Taglichtlampe referred to light sources between 5300 and 6500 K with specially adjusted spectrum. The different spectra of artificial light and daylight cause about some clothes indoors have other colors than in daylight.

The brightness of daylight is about illuminance levels between 1 to about 100,000 lux (lm / m ) ( photopic vision, tags marriages), the lower region is mesopic vision ( mixing area for night vision, in which the color perception does not work anymore precise ), also occurs glare one. The brightness increases from dusk until after noon strongly, and then decreases again rapidly. The human eye is sensitive over an enormous range, so this change in brightness are not perceived during the day in general.

The maximum of daylight is a light wavelength of about 555 nm (green light). Acts that daylight relatively evenly distributed throughout the hues, is that the spectrally dependent sensitivity of the eye is adapted to daylight. The ultraviolet component of solar radiation provides energy in the photosynthesis of plants and browning, the high infrared portion can act sun rays warming - both are hardly reflected by the environment, and through window glass largely filtered ( light absorption ), so you will be in the diffuse light the shadow and the interior is not brown and will hardly warmed: the daylight is then in its spectrum clearly be excluded. That one daylight and there still feels as warm, is that the cool blue portion of sunlight is scattered by Rayleigh scattering in the blue of the sky and the reflecting surfaces are primarily illuminated with red-yellow- shares.

CIE standard illuminants D in the CIELAB diagram

Rayleigh scattering, formation of the blue sky in daylight

Effects

Daylight is one of the main sources of light on the earth and for the daily lives of people. For chronobiology daylight is a key factor and will affect all metabolic processes in animal and plant life, animal migrations and the mood of the people. In architecture uses daylight to illuminate the interior of the building, plus there is specifically directed for optimal use (exposure, in contrast to the lighting).

In visual astronomy daylight is an obstacle: it is, after sunset, broken by scattering effect in the night side, so good freisichtige observation only about 1-1 ½ hours can be started after sunset with the onset of evening astronomical twilight - in terms of the Dawn analogously.

Daylight in the interior

Exposure through glass roof and pillars position Hong Kong Central Public Pier 9, 21th century

Incident sunlight through the slats of a barn