Daylight
Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunlight scattered or reflected by objects in outer space is generally not considered daylight. Thus, daylight excludes moonlight, despite it being reflected indirect sunlight. Daytime is the period of time each day when daylight occurs. Daylight happens as Earth rotates, and either side on which the Sun shines is considered daylight.
Definition
Daylight is present at a particular location, to some degree, whenever the Sun is above the local horizon.. However, the outdoor illuminance can vary from 120,000 lux for direct sunlight at noon, which may cause eye pain, to less than 5 lux for thick storm clouds with the Sun at the horizon, which may make shadows from distant street lights visible. It may be darker under unusual circumstances like a solar eclipse or very high levels of atmospheric particulates, which include smoke, dust, and volcanic ash.Intensity in different conditions
For comparison, nighttime illuminance levels are:| Illuminance | Example |
| <1 lux | Moonlight, clear night sky |
| 0.25 lux | A full Moon, clear night sky |
| 0.01 lux | A quarter Moon, clear night sky |
| 0.002 lux | Starlight, clear moonless night sky, including airglow |
| 0.0002 lux | Starlight, clear moonless night sky, excluding airglow |
| 0.00014 lux | Venus at brightest, clear night sky |
| 0.0001 lux | Starlight, overcast moonless night sky |
For a table of approximate daylight intensity in the Solar System, see sunlight.
Effects
is lighting an indoor space with openings such as windows and skylights that allow daylight into the building. This type of lighting is chosen to save energy, to avoid hypothesized adverse health effects of over-illumination by artificial light, and also for aesthetics. The amount of daylight received into an indoor space or room is defined as a daylight factor, being the ratio between the measured internal and external light levels. Artificial lighting energy use can be reduced by simply installing fewer electric lights because daylight is present, or by dimming/switching electric lights automatically in response to the presence of daylight, a process known as daylight harvesting.In recent years, work has taken place to recreate the effects of daylight artificially. This is however expensive in terms of both equipment and energy consumption and is applied almost exclusively in specialist areas such as filmmaking, where light of such intensity is required anyway. In some filmmaking locations, such as Sweden or Norway, there is too much light due to long summer days. As a result, in location films such as Marianne, night scenes have to be shot during daylight hours and are digitally altered later.