From: tmiller11147@verizon.net   
      
    wrote in message   
   news:844abad9-de3d-4b69-9e99-0a18410716aa@googlegroups.com...   
   > 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.   
   >> .   
      
   Another thought. The films used for automotive window darkening. I think   
   they are graded for optical density.   
      
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