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David R. Busse wrote:

> color 
> temps are hotter at high elevations,

This means closer to 5500K (bluer) at higher elevations, and closer to
5000K (warmer, or more orange looking) closer to sea level.

> and that shooting with a warming 
> filter...an 81, I believe...keeps shadows from going blue under these 
> conditions.
> 
> Never heard this before but it makes sense to me. 

There is more UV (blue) light getting through the atmosphere at higher
elevations, so the color temperature of the sunlight you work with up there
is 'cooler', or bluer, and this shows up on film (I like it though most of
the time).  This can be corrected to a degree with the use of a UV filter
(THAT'S what those things are really meant for!) which will cut off that
excess blue light over about 270nm (nonometers).  A warming filter can do
similar looking things, but warming filters work by changing the color cast
recorded on film, not by cutting out blue UV light.  A warming filter in
the mountains is technically too much, unless you are more used to the
color of the sky (more haze and pollutants) closer to sea level.  The sky
really is blue out in the country on a clear day!  

Dave

Dave Cohen
Photographer
Action Photographic Webmaster
[EMAIL PROTECTED]
http://www.anet-stl.com/acphotog/home/

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