Recommended light levels for common types of working activities

A minimum level of illumination is required to read correctly and without fatigue objects and thus perform correctly (and sometimes safely) the intended task .
The level of illumination required depends on the activity to perform
Light Level or Illuminance, is the total luminous flux incident on a surface, per unit area. Usually, standards and norms define the light levels by task. The difficulty is to define the space in which the task is to be performed. The amount of light being given off by a particular source, in all directions, is called luminous flux (or “luminous power” or “lux”) and is a measure of the total perceived power of light. It is measured in lumens.
Measuring Units Light Level – illuminance
Illuminance is measured in foot candles (ftcd, fc, fcd) (or lux in the metric SI system). A foot candle is actually one lumen of light density per square foot,one lux is one lumen per square meter.
• 1 lux = 1 lumen / sq meter = 0.0001 phot = 0.0929 foot candle (ftcd, fcd)
• 1 phot = 1 lumen / sq centimeter = 10000 lumens / sq meter = 10000 lux
• 1 foot candle (ftcd, fcd) = 1 lumen / sq ft = 10.752 lux
How to measure ?
A light meter (also called lux meter) is very useful. A light meter measures the amount of visible light illumination in a given area tested. Illumination is expressed in units of LUX (metric) orFoot candles (English).

optimum levels lighting