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10/16/2007 11:14:49 PM · #1 |
I need an old schooler to explain something to me:
Density = log(10) (Incident Light / Transmitted Light)
I can't seem to find an explanation of this formula and concept online anywhere... Maybe my google abilities are lacking tonight...
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10/17/2007 12:01:58 AM · #2 |
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. |
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10/17/2007 12:17:44 AM · #3 |
On a related note, does anyone know how the shade scale for welding goggles translates to the log scale?
As in, a shade #10 filter = ? on the log scale.
Thanks. |
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10/19/2007 11:45:36 PM · #4 |
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10/20/2007 12:14:55 AM · #5 |
| There's a table near the bottom of this page which at least lists the shades recommended for each type of welding operation, but I couldn't find anything which related the filter number to actual density on the log scale. |
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