The Human Eye Will Adapt to an Enormous Range of Illumination Levels

The human eye will adapt to an enormous range of illumination levels. The untrained eye cannot easily detect a 20% change in illumination levels. In a general office or home environment we read under levels ranging from 50 lux to 1000 lux. We can also read at night on the railway station platform with only 15 lux and conversely outside on a sunny day in illumination levels of 100,000 to 150,000 lux. However there is an optimum level which will produce the greatest "task efficiency" with the lowest practical illumination level. To ascertain the 'correct' illumination level for any given task extensive research has been carried out comparing various illumination levels with a person's task efficiency or work output under the different illumination levels. The results of these studies are the basis of the Australian/New Zealand Standard for Interior Lighting AS/NZS 1680 series. The illumination levels recommended in this standard are the minimum recommended illumination levels to be maintained that will permit consistently high task efficiency with comfortable intensity levels. As previously discussed, the first step in providing the correct solution is to identify the needs of the site. Minimum illumination levels for various applications should be checked with the Australian Standard and the type of luminaire which best suits the glare control limits required can be selected. The Standard generally recommends MINIMUM maintenance illumination levels only. It is also accepted that Corporate requirements, or unusual circumstances, may require higher levels in various situations. It is worthy of note that the highest recommended illumination level in the Interior Lighting Standard is 1600 lux, which is recommended for minute instrument workings inspection such as watch making. The key standards are: AS1680.1-2006, ‘Interior and workplace lighting - general principles and recommendations’ AS/NZS 1680.2 series, ‘Interior and workplace lighting - specific applications’ Source: ecosmartelectricians.com.au