If the density of the film is zero, it will transmit all the light which falls on it.
If the density is 1.0, it will allow 1/10 of the light to pass through.
Density 2.0 = 1/100 of the light to pass through, 3.0 = 1/1000, etc.
I have some high-contrast graphic arts film at work which reaches a density of over 4.0, meaning only 1/10,000 of the light passes through, making it safe to use to look at the sun during an eclipse. |
