Quote Originally Posted by Bill Burk View Post
So, the speed point would be..

125 = 0.8 / Hm
multiply both sides of equation by Hm... 125 Hm = 0.8
divide both sides of equation by 125... Hm = 0.8 / 125
Hm = 0.0064

Likewise, the metered point would be...
Hg = 0.064

Ten times... Seems extremely arbitrary or lucky to be such a round easy to remember number.
So it takes 0.064 Lux.Sec to produce a density of .10 plus fog on the film?