Re: Double Circular Polarizers for UV photography? Mounting an 18A ina camera?

[ADavidhazy <ANDPPH@xxxxxxxxxxxxxxxxxx>]

> I was wondering if anyone has every tried using two polarizer filters as an
> equivalent to an 18A filter (this is a UV filter that blocks all visible
> light, but allows UV and IR light to pass through)

I _think_that the problem with this is that polarizing filters typically are UV
absorbers themselves and when not they would extinguish UV as you cross them
much like they do light.          

> I was also wondering if anyone has ever custom cut an 18A filter (equivalent
> to a B+W 403)to approximately 24x36mm and mounted it in side a camera behind
> the mirror but infront of the shutter assembly?

While I have not heard of this (it does not mean it has not been done!) I have
heard of making a "fluorescent groundglass" ... installing such a device in the
camera allows you to see the UV scene with an 18A over the lens. I have done 
this myself but the limitation I have run into is that the fluorescence is very
dim and the image hard to see. This technique was described many, many years
ago in Technical Photography magazine or a similar one.

Andrew  o o  0 0 o . o  Davidhazy, Imaging and Photo Tech
         \/\/\/\/\/\/          http://www.rit.edu/~andpph
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