Re: Cheap source for UV transmitting filters?

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On 12 Mar 99 at 9:58, Rolland Elliott wrote:

> Does anyone know of a cheap source for UV transmitting filters for UV
> photography?
> 
> Hoya has discontinued their UV filter the U360, and B+W has
> discontinuted their 18A equivalent the 484 filter.

Are you sure about that?
Could that be an US-market or stock issue?
Either B+W or Heliopan will mount *any* type of Schott glass on
request/custom-order....and while 403 is nothing more than Schott
UG1, 484 is nothing more than UG3....and it's very hard to believe
Schott wouldn't make those anymore....
 
> I think there are only three filters available for UV photography now:
> 
> B+W makes their 403 filter which lets UV and some visible light
> through, so it's not quite equivalent to an 18A filter which blocks
> all visible light.

I am afraid you are getting into marginal differences here....18A is not 
100% opaque to the naked eye in broad daylight either (shielding eye 
provided)....I would rate it equivalent in visible transmission 
intensity (not color!) to 88a.
Also note that according to Kodak charts, #18 has a near 1-10% 
transmission dip between 700 and 800nm....which can clearly be proven 
with an IR-only source like a light bulb.
 
> Tiffen makes an 18A filter.
> 
> Kodak makes an 18A filter, which is square.  

Yup, and mounted in a metal frame. Hand-written coding on the 
box....pretty slow moving item I guess....:-))
 
> All of these filters are VERY EXPENSIVE, and must be mail ordered in
> the US.  
> 
> There must be other sources, that are cheaper.  Are their any cheap
> plastic or gel alternatives?  Any homemade soultions?

Nope, only glass will do what you are looking for....have seen that 
question pop up several times in sci.optics over the years, but no 
one ever mentioned an alternative to (expensive) glass.... 


--                 
Bye,

Willem-Jan Markerink


      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]
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