Kruithof curveThe Kruithof curve describes a region of illuminance levels and color temperatures that are often viewed as comfortable or pleasing to an observer. The curve was constructed from psychophysical data collected by Dutch physicist Arie Andries Kruithof, though the original experimental data is not present on the curve itself. Lighting conditions within the bounded region were empirically assessed as being pleasing or natural, whereas conditions outside the region were considered uncomfortable, displeasing or unnatural.
SkylightA skylight (sometimes called a rooflight) is a light-permitting structure or window, usually made of transparent or translucent glass, that forms all or part of the roof space of a building for daylighting and ventilation purposes. Open skylights were used in Ancient Roman architecture, such as the oculus of the Pantheon. Glazed 'closed' skylights have been in use since the Industrial Revolution made advances in glass production manufacturing. Mass production units since the mid-20th century have brought skylights to many uses and contexts.
LuxThe lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a model of human visual brightness perception, standardized by the CIE and ISO.
