Neutral Density Math

[Colin Kaminski]

How does Neutral Density Math work?

Is it a power? So ND 2 is 1/100 of the light and ND 3 is 1/1000?

TIA

[MichaelH]

http://en.wikipedia.org/wiki/Neutral_density_filter

[Colin Kaminski]

Thank you!

Fractional Transmittance = 10^-OD

Where the filter is listed as OD.

[Ed Wesly]

Other landmarks along the ND filter trail are: .3 = 1/2, .6 = 1/4, .9 = 1/8. 1.0 = 1/10