[LargeFormat] RE: IR filters

[Clive Warren]

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