IN ITS RELATION TO THE EYE. 



463 



this quantity appears, is plotted against the results of the test. This, 

 it will be remembered, was true also of the work of the preceding 



70 



50 



30 



Chart VI. (Translucent Direct Reflectors Differing in Density.) Show- 

 ing the tendency of the six types of translucent direct reflectors to cause loss 

 of power to sustain clear seeing. In Curve A, percentage loss in power to 

 sustain clear seeing after work is plotted against ratio of highest brightness 

 of reflector to brightness at point of work; in B, against ratio of highest 

 brightness of reflector to average brightness; in C, against ratio of highest 

 brightness of reflector to darkest surface in field of view; in D, against aver- 

 age brightness; in E, against ratio of average brightness to brightness at 

 point of work; and in F, against ratio of average brightness to darkest sur- 

 face in the field of view. 



