On Monday, September 29, 2014 8:21:34 PM UTC-4, Tom Miller wrote:   
   >  wrote in message   
   >   
   > news:61fa8ed9-ce12-48fb-a260-b281e5d82d7f@googlegroups.com...   
   >   
   > > Hi All,  We've are using these 0.7ND kodak wratten  #96 ND filters.   
   >   
   > > We can only get them from Tiffen.   
   >   
   > > (so maybe the name should be Tiffen Kodak Wratten...)   
   >   
   > > I went to reorder and found that the ~1.5" x 1.5" pieces we use in lots of   
   >   
   > > 8 are going to be ~$10 each.   
   >   
   > > I'm contemplating a letter to tiffen, without much hope.   
   >   
   > > So I'd really like another solution.   
   >   
   > > These are used in student labs to attenuate a diode laser.   
   >   
   > > (I think there is ~3-5mW (typical) but I'd have to measure.)   
   >   
   > > There's a "real" glass 1.0 ND filter, to suck up most of the laser power.   
   >   
   > > And then a holder for the above pieces of plastic put in 35mm slide   
   >   
   > > projector mounts.  At 780 nm they are really 0.5ND filters, which seems   
   >   
   > > like a nice number.   
   >   
   > > Two gives you about a factor of ten.   
   >   
   > > (Sorry for the long winded wind up.)   
   >   
   > >   
   >   
   > > Is there some other absorptive piece of something I could use?   
   >   
   > > Not too expensive and reproducible.   
   >   
   > > Most plastics used in lighting become transparent beyond 700nm or so.   
   >   
   > > Yeah I've thought about reflective things.   
   >   
   > > It seems too dangerous for a student lab.   
   >   
   > > (The reflective filter can spray most of the laser power around the lab.)   
   >   
   > > But if you have a reflective thing for ~$1 per square inch ~0.5ND...   
   >   
   > >   
   >   
   > > George H.   
   >   
   > >   
   >   
   > You might browse around in a welding supply store or on the net. They have   
   > graded filters for different weld processes on up to ND12 or more.   
   >   
   >   
   I'll give a look see, I'm guessing nothing on the low end.  ND 0.5 is the same   
   as an eye squint to a welder.  I was thinking I could get something from   
   China.. sigh.   
      
   George H.   
   > .   
      
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