Re: mired

[T3D George Gioumousis <georggms@xxxxxxxxxx>]

T3D john bercovitz wrote
> I guess I must need to think about this but I still don't see how 
> a mired _could_ work.  I guess I'm supposing that the filter exactly
> raises a perfect black body curve so many degrees.  Such a filter
> would have to be different for every in and out temperature.  What
> the mired must do is give a new effective temperature not a new
> black body temperature?

I think it goes like this, I think:

	The distribution in energy of a black body is
		exp(E/(kT))
	where E is the energy of the photons, T the 
	absolute temperature, and k is a constant.
	Filters are multiplicative, and if the filter
	has the same form, but with T0 intstead or T
	then the resulting distribution with, say T1,
	where
		1/T1 = 1/T + 1/T0

I can't quite believe _filters_ have a black body shape, but then
I don't really believe all light _sources_ have a black body
distribution. Of course sodium, mercury, and fluorescent lights
don't, but then open shade doesn't either. The blue color of
the sky is due to Rayleigh scattering, which has a 1/lambda
dependence on the wave length, lambda, of the light.

-- 
George Gioumousis           /---\        |       /---\ 
                             o o         |       o o  
georggms@xxxxxxxxxx           |          |         |   
(415) 494-6276              \===/        |       \===/ 


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End of TECH3D Digest 20
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