Unexpected result with Red 25 filter

[Lee L]

Originally Posted by keithwms

the Rayleigh scattering associated with haze goes as 1/(wavelength)^4, so in other words longer wavelengths scatter much less in the atmosphere and a red filter will thus "see" less haze.

Which is why fog lights for driving are often filtered to yellow and part of the reason that the French drive with yellow headlights. I also use this info on Rayleigh scattering to fight installation of the newer full spectrum outdoor lighting, which has a much more deleterious effect on night skies than the yellower sodium light sources.

<end of OT extension of tedious lecture>

Lee

[rmolson]

Originally Posted by Lee L

I read something about a year or so ago about using a Wratten 25 to reduce contrast on interior shots with bright windows. Can't recall where right now, but the results were initially unexpected, then exploited to reduce contrast in similar circumstances where it was needed. The source I read could easily have been older.

Lee

I remember reading the same article. I think it might be because the interior light was artificial tungsten but the outside light was high in blue.The red filter tended to block that light and saw only the tungsten softer light.at a considerably longer exposure which also tends to lower contrast At least it sounds good.