brightness与luminance

Luminance is a photometric [光度] measure of the luminous intensity [发光强度] per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls within a given solid angle [立体角]. Brightness is the term for the subjective [主观] impression of the objective [客观] luminance measurement standard. 立体角是平面角在三维空间中的类比。

The SI unit for luminance is candela (Latin candle) per square metre (cd/m² 坎德拉/平米), as defined by the International System of Units (SI is from the French Système international d'unités) standard for the modern metric system. A non-SI term for the same unit is the nit [尼特].

The lumen (symbol: lm 流明) is the SI derived unit of luminous flux [通量], a measure of the total quantity of visible light emitted by a source per unit of time. Prior to 2019, the definition was based on the candela. The lumen is related to the candela as:

1 lm = 1 cd ⋅ sr

A full sphere has a solid angle [立体角] of 4π steradians [立体弧度], so a light source that uniformly radiates one candela in all directions has a total luminous flux of:

1 cd × 4π sr = 4π cd⋅sr ≈ 12.57 lumens

Lumens are related to lux [勒克斯] in that one lux (lx) is one lumen per square metre:

1 lx = 1 lm / m²

下面左图是照度计，右图是功率计。选购台灯发愁？这篇桌面照明方案助你一臂之力

夏季阳光直射时，光照强度可达6万～10万lx，没有太阳的室外0.1万～1万lx

夏天明朗的室内100～550lx，夜间满月下为0.2lx

一般建议小孩子看书时的照度在300-500 lx

六级/考研单词: luminous, emit, subjective, derive, sphere, radiate

标签：luminance,brightness,per,cd,lx,luminous,candela,unit
来源： https://www.cnblogs.com/funwithwords/p/16524488.html