denomination of Schott/Heliopan filters

[Clive Warren <cocam@xxxxxxxxxxxxxxx>]

>Date: Sun, 02 Apr 2000 11:57:54 +0200
>From: Eckhard Stephan <eckhard.stephan@xxxxxxxx>
>Subject: denomination of Schott/Heliopan filters
>
>Hello everyone,
>
>during a discussion between Gavin Wrigley and me about his new IR pages
>we came to talk about the denominations used by Schott / Heliopan for
>their glass filters. I always thought, that in names like RG-XXX XXX
>stood for the filter's cut-off frequency. Meanwhile I'm not so sure
>about that anymore. Maybe someone could clarify this?
>
>Thanks in advance,
>
>Eckhard

Hello Eckhard,

At the risk of sounding like a scratched record (guess that should be CD
now!), take a look at the Infrared FAQ (URL in sig. file) section 12.
"Which Infrared Filters?".  There is a table there with all of the filter
information against the Wratten values. I have also coloured the details to
indicate the spectral characteristics of the filters as seen by the human
eye.

The Heliopan filter numbers do not make a lot of sense in the infrared
ranges, however the Schott numbers do refer to spectral transmission.


All the best,

             Clive   http://www.cocam.co.uk
                     Photographic Services, Filters and Equipment, Infrared FAQ
                            http://clive.bel-epa.com
                            Adventures in Cyberspace - Digital Art and Photos


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