lumimäärästä

Luminäärä, often translated as luminous flux, is a fundamental concept in photometry. It quantifies the total amount of visible light emitted by a source, or passing through a surface, per unit of time. Unlike radiant flux which measures all electromagnetic radiation, luminous flux specifically considers the human eye's sensitivity to different wavelengths of light. The standard SI unit for luminous flux is the lumen (lm).

The lumen is derived from the candela, the SI unit of luminous intensity. One lumen is defined as the luminous flux emitted by a point source of one candela within a solid angle of one steradian. This relationship highlights that luminous flux is a measure of the total "lightiness" of a source, taking into account how that light is distributed in space.

Various factors influence the luminous flux of a light source. For instance, the wattage of a light bulb is often correlated with its luminous flux, with higher wattage bulbs generally producing more lumens. However, efficiency also plays a crucial role; more efficient bulbs, like LEDs, can produce significantly more lumens per watt than older incandescent bulbs. When comparing light sources, luminous flux is a more accurate indicator of perceived brightness than power consumption alone. Understanding luminous flux is essential for applications ranging from lighting design to product specifications.