threshold

[Goss, Bill]

In the intro text I am using (Weiten) there is a statement that the absolute
threshold for human vision is " a candle flame seen at 30 miles on a dark,
clear night."  Can someone tell me how this was determined?  Did someone
really do a field study on this?
Thanks

---------------------------------------------------
Bill Goss                               phone:(250) 489-2751, ext. 324
College of the Rockies          [EMAIL PROTECTED]
Box 8500
Cranbrook, BC, Canada
V1C 5L7