Glancing Light (临界光的影响)
Glancing light (or critical light) is a phenomenon that occurs when light strikes a plasterboard surface at an acute angle, casting a shadow that highlights any irregularities in the surface. On plasterboard walls and ceilings this can make the surface look uneven and highlight the appearance of joints.
临界光（或称为掠射光）是指当光线以锐角射向石膏板表面时产生的一种现象，它投射出的阴影会凸显出表面的任何不平整之处。(如下图所示) 在石膏板墙和天花板上，这种情况可能会致使表面看起来不平整，并且突出显示接缝的模样。
Consideration to Minimise Glancing Light (考虑减少临界光的影响)
It is critical to consider how to minimize the impact of glancing light during the design phase, which allows us to make effective choices that significantly reduce its impact.
在设计阶段，考虑如何将掠射光的影响降至最低是至关重要的，这使我们能够做出有效的选择，显著减少其影响。
The installation of plasterboard walls and ceilings should also be taken into account, as there are many design and installation options that can significantly affect the appearance of the surface.
石膏板墙和天花板的安装也应考虑在内，因为有许多设计和安装选择可能会显著影响呈现效果。
Laying the plasterboard so that the long joints are parallel to the direction of the light helps mitigate the effects of glancing light. It is also possible to use longer sheets to reduce the number of butt joints.
铺设石膏板，使长接缝与光的方向平行，有助于减轻反光的影响。也可以使用更长的板材来减少对接接头的数量。
Artificial or Natural Light (人造光或者自然光的影响)
Methods to minimise glancing / critical lighting effects from artificial lighting sources (减少来自人造光源的临界光照影响的方法)
The following lighting schemes will provide soft light and reduce the visibility of surface unevenness:
以下照明方案将提供柔和的光线，减少表面不平整的可见性：
• Shaded batten holder light fittings. 阴影板条支架灯具
• Ceiling mounted pendant lights. 天花板吊灯
• Embedded ceiling lights, such as downlights and recessed fluorescents. If they cause critical light, they should not be installed close to the walls.
嵌入式天花板灯，如筒灯和嵌入式荧光灯。如果它们会导致临界光，则不应靠近墙壁安装。
• Consider using more low-intensity lamps at fixed intervals and ensure that the illuminated areas overlap. This will improve the environment, reduce the visible impact of visible light, and minimize the shadows that might be generated by single rows or single light sources.
考虑在固定的间隔使用更多低强度的灯，并确保照明区域重叠。这利于改善环境，减少可见光的可见影响，并最大限度地减少可能由单排或单个光源产生的阴影。
• For feature lighting like spotlights, allow the light to hit the surface at a large angle of incidence in order to minimize the highlighting of imperfections.
对于像聚光灯这样的特色照明，允许光线以较大的入射角照射到表面，以尽量减少瑕疵的凸显。
• In a space with generally low levels of light, do not place a single or isolated unshaded light source close to the wall or ceiling.
在整体光线水平较低的空间中，不要将单个或孤立的未遮光光源靠近墙壁或天花板放置。
• Do not use uplights, wall-washers and spotlights in the smooth areas of the wall to eliminate light being emitted at a glancing angle to the surface.
避免在墙面平滑的区域使用上照灯、墙面洗墙灯和聚光灯，以防止光线以掠射角照射到表面。
• A better approach is to install fluorescent lights about 450mm above the ceiling to achieve a more even distribution of light.
更好的是将荧光灯安装在天花板下方约 450 毫米处，因为这样会使光线分布更均匀。
• When installing ceiling mounted fluorescent lights, it is recommended to position the light fittings over the long edge joints. Refer to the following illustration.
在安装吸顶式荧光灯时，建议将灯具定位在长边接缝之上。请参阅下图正确示意图。
Methods to minimise glancing / critical lighting effects from natural lighting sources (减少自然光源造成的临界光照效果的方法)
• Do not install the window glass as high as the ceiling. 不要将窗户玻璃安装到与天花板同高。
• Avoid placing windows or glass doors right next to the end of the wall. 避免将窗户或玻璃门紧挨着墙边。
• Provide sun shades over the windows and glass doors. 在窗户和玻璃门上安装遮阳帘。
• Set the windows as recessed ones to prevent direct sunlight from shining on the walls. 将窗户设置为嵌入式，以避免阳光直射到墙壁上。
Reference:
参考文献：
- CSR红皮书 – 住宅和商业系统