Luminance & Illuminance 亮度和照度
Luminance 亮度
Glare 眩光
当谈及眩光，直接眩光和反射眩光是有区别的。直接眩光1主要来自灯具，反射眩光主要是指来自水平面2和垂直面3的视觉显示终端(VDT, Visual Display Terminal)反射的。
With regard to glare a distinction is made between direct glare, caused primarily by luminaires (1), reflected glare in the case of horizontal visual tasks (2) and reflected glare in the case of vertical visual tasks, e.g. at VDT workstations (3).
视觉显示终端上的眩光限制：推荐视觉显示终端的区域选用的灯具截光角至少30度。
Glare limitation at VDT workstations: for areas with VDT workstations a cut-off angle α of at least 30° is recommended.
对于可调节的灯具，如射灯和可调节方向的灯具，眩光也受灯具照明方向的影响。眩光将主要来自灯具调节的方向不正确。
对于固定位置的灯具如下照灯或灯光结构，则需要识别直接眩光和反射眩光。直接眩光的案例中，眩光限制的平直由灯具的光分布决定，对于改进眩光控制，下照灯的截光角越大，灯具提供的视觉舒适越大。
In the case of adjustable luminaires, such as spotlights or directional luminaires, glare also depends on the light distribution of the luminaire. Glare primarily occurs if the luminaire is not correctly adjusted. In the case of stationary luminaires, such as downlights or light structures it is necessary to distinguish between the elimination of direct glare and reflected glare. In the case of direct glare, the quality of glare limitation depends on the light distribution of the luminaire. The greater the cut-off angle in downlights, the greater the visual comfort provided by the luminaire due to improved glare control.
Standards 标准
通过将视线反射投影到天花上可以定义出一个区域，在这个区域内的灯具可能导致明暗对比的负面的影响。
By projecting the field of vision onto the ceiling surface it is possible to define the area in which the luminaires may have a negative influence on contrast rendering.
工作区域的照明是有标准可参考的，标准规定了最小的截光角或灯具的极限截光范围。对于视觉显示终端工作区又有特定的要求。关键的区域可以这样定义，将工作面用镜子覆盖用户能看到的那部分的天花。对于有镜面反射器的灯具，光束的截光角越大，直接眩光控制的越好。标准的截光角是30度和40度。
UGR（统一眩光值）系统用来评价和控制室内空间的直接不舒适眩光，UGR的值受光源的亮度，被视见的大小（立体角），位置以及背景环境亮度的影响。一般在10到30区间，越小UGR值越少的眩光。
Standards exist for the lighting of workplaces, which stipulate minimum cut-off angles or highest permissible luminances in the cut-off range. For workstations with VDTs there are specific requirements. The critical area can be defined as that portion of the ceiling which is seen by the user in a mirror covering the working area. In the case of luminaires with mirror reflectors direct glare control improves the greater the cut-off angle. The standard cut-off angles are 30° and 40°.
The UGR (Unified Glare Rating) process is used to evaluate and limit the direct discomfort glare in indoor areas. The UGR value is influenced by the light source’s luminance, its visible size (solid angle) and its position (position index), as well as the luminance of the background. It is usually between 10 and 30. The smaller the UGR value, the less the glare.
Illuminance 照度
CIE对不同活动推荐的照度水平
Recommended illuminance level E according to CIE for various activities
视觉表现一般随着照明水平的增加而提升。当高于1000lux的后增长较慢，超高的照度水平时随着眩光的效果还会开始降低。
然而，遵循一套不变的照度水平规则对实际实践几乎不起什么作用。照度不是多少光通量落到指定的表面而在眼睛里产生的画面，而是光是通过表面发射、传播或反射。视网膜上的画面是由整个感知的对象的明暗造型创造的，这既包括灯光也包括对象。
Visual performance generally improves sharply as the illuminance level is increased. Above 1000 lux, however, it increases more slowly, and at extremely high illuminance levels it even starts to decrease due to glare effects.
However, following a set of fixed rules for illuminance levels gives little consideration to actual perception. It is not the luminous flux falling on a given surface – illuminance – that produces an image in the eye, but the light that is emitted, transmitted or reflected by the surfaces. The image on the retina is created entirely by the luminance pattern of the perceived objects, in the combination of light and object.