From: rrllff@yahoo.com   
      
   On Monday, December 7, 2015 at 4:18:28 PM UTC-5, Phil Hobbs wrote:   
   > Hi, all,   
   >   
   > Back in the day, Corning used to make sharp-cut red filters with   
   > spectacularly low autofluorescence compared with Hoya and Schott ones.   
   > H & S seem to light up like a Christmas tree at a wavelength about   
   > 50-100 nm to the red of the edge, which is very inconvenient at the moment.   
   >   
   > Corning doesn't make coloured glass filters any more.   
   >   
   > Two questions for the assembled multitude:   
   >   
   > 1. Does anyone know who they sold the line to. if anybody, and if   
   > they're still available?   
   >   
   > 2. Any wisdom on 800-nm-ish sharp cut longpass filters with super low   
   > autofluorescence?   
   >   
   > Thanks   
   >   
   > Phil Hobbs   
   > --   
   > Dr Philip C D Hobbs   
   > Principal Consultant   
   > ElectroOptical Innovations LLC   
   > Optics, Electro-optics, Photonics, Analog Electronics   
   >   
   > 160 North State Road #203   
   > Briarcliff Manor NY 10510   
   >   
   > hobbs at electrooptical dot net   
   > http://electrooptical.net   
      
   That's interesting.  I would expect all the manufacturers to use the same   
   dyes, especially "back in the day".  Do you have any theories as why the   
   Schott and Ohara filters fluoresce? Seems very odd, and of course very   
   annoying.   
      
   http://www.richardfisher.com   
      
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