ILLUMINATION 365 



ILLUMINATION 



Method of Illumination. Illumination should be by transmitted, 

 dissipated, and reflected light. If the light is glaring and too bright, 

 it blinds the eyesight. Not only is the decorative value of a room 

 destroyed but the sense of comfort and repose is lacking in offensive 

 white light. 



Amount of Illumination. The well-known sleepiness of church- 

 goers of olden times was often due to eye fatigue from the harsh light 

 in front. Many people suffer from theater headaches and moving 

 picture headaches for the same cause. 



Sleepiness comes on very readily when reading by artificial light 

 because of eye strain brought about by the light used. The brilliancy 

 of any light should not exceed 4 to 5 candle power per square inch, 

 and may be as low as from ^ to &. One should never read in any 

 light which causes discomfort to the eyes. 



The following table vitll give some idea as to the amount of 

 brilliancy in candle power per square inch of some of our methods of 

 lighting. Bear in mind that the safe range of candle power for 

 comfort is from 1 to 5 candle power per square inch. 



Source of Light. Candle Power per Sq. In. 



Candle 3 to 4 



Oil Lamp 3 to 8 



Gas Flame 3 to 8 



Welsbach gas mantle 20 to 50 



Carbon filament light 375 to 400 



Tungsten electric light 1000 to 1500 



Direct Lighting. When the rays of light from a lamp are reflected 

 in one general direction, usually downward, it is said to give direct 

 light. This is accomplished by the use of a dense shade of metal, 

 glass or silk. The usual type of reading lamp is an example of direct 

 lighting. 



Semi-direct Lighting. Sometimes translucent reflectors which 

 permit some of the rays to pass through upward, yet reflect the 

 majority of the rays downward, are used. Whenever reflectors of 

 this type are used, semi-direct lighting is produced. 



