== Illumination ==
Illumination is measured in lumensusing an illuminometer such as [http://www.sekonic.com/products/i-346/overview.aspx Sekonic]. The SI measurement of illumination is lux, or one lumen per square metre (about 1/10 foot-candle). A lumen is the amount of light falling on a surface. A foot-candle is one lumen distributed over one square foot.
The illumination required for casual reading is 200-550 lumens/sq metre. The standard for office desks is 500 lumens. Some general guidelines are given in the below table. These are generally in excess of [https://www.abycinc.org/ ABYC] standards but you should check when you build.