<prompt> For satisfactory vision the minimium illumination accepted is -15 to 20 foot candles30 to 40 candles40 to 50 candles70 to 90 candles  <response>: An illumination of 15 to 20 foot-candles is accepted as a minimum basic requirement for satisfactory vision. 1 FC 10.76 Lux Parks Textbook of Preventive and Social Medicine, 25th Edition, Pg 799 