A unit of measurement of the amount of brightness that comes from a light source. This darkening can be compensated by increasing the brightness of the projector light source. It is sufficient that stray light from a bright light source enters the lens. One candle served as a light source. Radiosity takes into account the energy given off by surrounding objects and the light source. This is ideal in space, where the Sun is a single light source. Real colors are colors that can be produced by a physical light source. The setup consists of two linear polarizers and a light source. Thus the color one sees depends on the spectral composition of the light source. The idea of using quantum dots as a light source emerged in the 1990s. A given photoreceptor responds to both the wavelength and intensity of a light source. Luminous efficacy is a measure of how well a light source produces visible light. Various effects can be achieved by moving both the puppets and the light source. Modulation can be achieved by the light source directly. Shortly thereafter headlamps using the new light source were introduced in Europe.