The degree of luminosity required in a room depends on the tasks that will be carried out in that space. The higher the level of precision needed, the greater the intensity of light should be. However, when the activities that take place in a given space do not call for a high level of precision, there is no need to increase the luminosity. So, before selecting a particular lighting system for a designated space, make sure to examine the types of visual tasks that will be performed there.
The Illuminating Engineering Society of North America (IESNA) has designated seven degrees of luminosity based on the visual requirements needed to accomplish a designated task in each space. Following are the recommendations on the degrees of luminosity in foot-candles and in lux for each type of visual task.
Orientation and Simple Types of Visual Tasks
In this category, visual accuracy is largely unimportant. Reading and visual inspection are rarely performed. The spaces are most often public. High-intensity lighting is not essential. In this group, we list hotel hallways, transition spaces between two areas as well as public spaces.
Common Types of Visual Tasks
In commercial, industrial and residential spaces, visual accuracy is important because tasks are performed on a regular basis. Various types of lighting systems should be considered in order to diversify the light source according to the exactness of the task at hand. A high degree of luminosity should be used for tasks that feature critical components with very little contrast, or small sized elements such as those found in a clothing manufacturing facility.
Special Types of Visual Tasks
For these tasks, good visual accuracy is critical. These tasks are highly technical and may, on occasion, require particularly fine details and a very small or very low contrast. A localized source of lighting is recommended in proximity to the work station to ensure broad lighting of the spaces in which these specific tasks are performed. For example, spaces where fine jewellery is made or where works of art are in the process of being restored.
How to Measure LightingDiscover the significance of foot-candle and lux as well as to learn how to measure each component.