For satisfactory vision the minimium illumination accepted is -
15 to 20 foot candles
30 to 40 candles
40 to 50 candles
70 to 90 candles
An illumination of 15 to 20 foot-candles is accepted as a minimum basic requirement for satisfactory vision. 1 FC = 10.76 Lux Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 799
Environment and health