Double Circular Polarizers for UV photography? Mounting an 18A in a camera?

["Rolland Elliott" <rolland_elliott@xxxxxxxxxxx>]

Hi,

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 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?

I'm trying to get into some UV action flash photography, but the most 
difficult problem is that one cannot compose or focus through a visibly 
opaque 18 A filter! By using two circular polarizers, one could simple turn 
the polarizer right before exposure to block visible light.

As far as the other solution of mounting a filter between the mirror and 
shutter, the custom cut filters are expensive. See below for pricing from 
Rolyn Optics for 25mm x 37mm x 1mm filters
1pc    #65.1015    cut to 25mm x 37mm $130.25 ea
1pc    #65.1005    cut to 25mm x 37mm $157.50 ea

Both of the above filters are very close to an 18A filter.

Or I was thinking I could just buy a regular round filter and cut it down 
myself. B+W's filters are only about 2.2 mm thick and I should be able to 
squeeze one in a mirror box after cutting it down.  However the only kind of 
glass I've ever cut is window pane glass and filter glass is very different. 
Do you think using a glass etcher would work on cutting up a round filter to 
a rectangular shape? I have a Dremel rotary tool that might be useful.  
Cutting it down myself, would cost me about 1/2 as much as ordering a custom 
filter (unless of course I broke the filter in the process) then the money 
would be wasted.

Any insight or comments would be appreciated.  I know there aren't many UV 
shooters on this list, so maybe I'm just rambling.

Peace Rolland Elliott




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