Nick, You sure about that?
Originally Posted by Nick Zentena
I believe a "Factor" of 2 would be 1.4 stops and a factor of 1 would be 1 stop. I don't know about Hoya but I have a little booklet from B+W that says their ND Filters:
101 2X factor = 1 Stop
102 4X factor = 2 Stop
103 8X factor = 3 Stop
106 64X factor = 6 Stop
110 1000X factor = 10 Stops
Seems their ND Filter # hold a clue to Stops. But this is not true of their Contrast Filters where the square root of the X factor determines the Stops.