[LargeFormat] RE: IR filters

[Marc Falcone]

Hello Clive,

You can see all the Schott glass filters spectral curves at

http://www.noao.edu/kpno/filters/sgt.html

Here is the exact address for the RG-9:

http://www.noao.edu/kpno/filters/sgt/127_sm.gif

The left part of the curve likes that of RG-715, (or rather "RG-720") except 
that it doesn't turn toward shorter wavenlenths as the RG-715 does, but 
keeps the wavenlenght even up to density 5. It's for this reason that RG-9 
is suitable for direct IR viewing.
My photos are not yet available on the net at this time.

Marc
>From: Clive Warren <cocam@blueyonder.co.uk>
>Reply-To: largeformat@f32.net
>To: largeformat@f32.net
>Subject: Re: [LargeFormat] RE: IR filters
>Date: Wed, 19 Jun 2002 00:48:59 +0100
>
>At 1:07 am +0000 16/6/02, Marc Falcone wrote:
>>Hi, Clive,
>>The RG-9 is a Schott-glass filter, it has no a 3 digits designation 
>>because it is not a long pass filter, but a band pass filter, so the 
>>designation "RG-9" is  probably because the central wavelenght is 900 nm. 
>>But the band is very large and don't affects IR films a lot. It can be 
>>compared to a "RG-730" which transmission percentage begins to drop 
>>progressivly from about 850nm and above, but the loss is not significative 
>>for normal IR film, unless it is a special long wave IR film (1200 nm) or 
>>digital backs. This is the very best filter for direct visualisation of 
>>short IR, you can see through it and see very brightly the near IR. It is 
>>available in 1mm, 2mm or 3mm thickness. They are available at 
>>www.schottglasstech.com  .I have especially ordered a piece of RG-9 in 
>>diameter 82mm, 2mm thick that I have mounted in a 86mm filter ring. For 
>>direct IR viewing, ready made pieces of 2" x 2" are available in 1, 2 or 
>>3mm thick. The original glasses are 6 1/2 by 6 1/2 square and they can cut 
>>them to every shapes and size you want. I paid US$ 250 for my 82mm 
>>circular piece, but ready made 2"x2" are about US$ 50 per piece.
>>
>>Marc
>
>Hello Marc,
>
>Thank you for the information. Would love to see that filter sometime. A 
>little too expensive for my taste but can see why you went for it.
>
>Do you have any of your photos on the web?
>
>Cheers,
>        Clive
>
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