## Calculation of daylight coefficients

The daylight coefficient D as the relation of interior illuminance to exterior illuminance based on Equation (8.1) is defined as standard for two measuring points at a height of 0.85 m, and 1 m away from the side walls. The daylight coefficient consists of a skylight proportion Dsky, a proportion of diffuse reflection of shading […]

## Daylight distribution in interior spaces

With the asymmetrical luminance distribution of the Moon and Spencer sky, the daylight distribution in the interior can now be calculated. First, as an overview, an illustration will be made of which zenith angle areas the main part of the light-flux falls from, onto a vertical or horizontal glazing surface, in order to make simple […]

## Light measurements

The human eye is capable of comparing illuminances of adjacent surfaces with an accuracy of about 2%. This was quantitatively first used in the so-called grease photometer of Bunsen, where luminous intensities were determined by shining two light sources from opposite sides on a paper screen partly covered with grease. If one light source has […]

## Sky luminous intensity models

To calculate the daylight distribution in a room, models of the luminous intensity distribution of the sky are required. From the luminous intensity distribution, the effective surface and the solid angle, the light flux onto any recipient surfaces, for example windows, can then be calculated. As the simplest model, the illuminance of the sky is […]

## Distribution of the luminous intensity of artificial light sources

The luminance of lamps or lights is rarely constant in all directions in space. Luminous intensity distributions are indicated by the manufacturers in polar diagrams in different sections. Usually the absolute luminous intensity in candelas refers to a fixed lamp light-flux. If in Equation (8.14) the luminance of the sender surface is replaced by the […]

## Luminance and adaptation of the eye

The luminance of sources of light or radiation-reflecting surfaces vary over a very wide range of values. Table 8.3: Luminances of sources of light. Light source Luminance [cd/m2] Sun, values depending on sun height 600 000 to 1 600 000 000 Clear sky 2000-12 000 Overcast sky 1000-6000 Lightbulb 20 000-50 000 Compact fluorescent lamp […]

## Luminance and illuminance

The light flux onto a surface and thus the illuminance Ev, defined as light flux per square metre, can in the simplest case be calculated, at a given solar irradiance, directly from the radiating power and the photometric radiation equivalent. For the solar irradiance one usually proceeds from an isotropic diffuse energy distribution. Since luminance […]

## Artificial light sources

50% of all artificial light sources are fluorescent lamps, consisting of a glas tube with two wolfram electrodes with an emitting surface at the ends. The gas filling is a mixture of rare gases such as argon or krypton (at a pressure of 70 Pa) and Hg (at 1 Pa pressure). The Hg atoms emit […]