This is kind of off topic, but since the news was reported on this site, I thought I'd ask the question.

Sony indicates that if the IR nightvision on their videocams is turned on in daylight, and a "special filter" is used, you effectivly get "x-ray" vision that can see through some types of fabric.

Does anyone know what type of filter to use??

I recently bought a Sony videocam with IR night vision, and I'm dying to know!! For sientific purposes only, I assure you...........

Thanks

-- Jeff Henderson (jphender@ix.netcom.com), August 18, 1998

Answers

Well, strictly in the interests of science...

I finally found my Kodak "Photographic Filters Handbook" this morning. I think what you'll want is one of the filters that blocks visible light, but lets IR pass through. Kodak makes a range of these with different wavelengths. The "nominal" filter seems to be the Wratten number 87, which cuts out 10% of the light at a wavelength of 760 nm (nanometers) This should be just outside the normal visual range. The 88A has a much sharper cutoff, but starting at a shorter wavelength, around 720nm, which is closer to the visible spectrum. I would guess the Wratten 87 would be the best bet. (The 87C cuts out everyting "redder" than 800nm, but that's getting pretty far into the IR, and I don't know what wavelengths the "Night Shot" works at.

Hope this helps - If you get in trouble, you didn't hear it here!

Dave E.

-- Dave Etchells (web@imaging-resource.com), August 20, 1998.