IR Filter

finn

Newly Enlightened
Joined
Sep 8, 2007
Messages
56
Location
Germany

PhotonWrangler

Flashaholic
Joined
Oct 19, 2003
Messages
14,412
Location
In a handbasket
Hmm... methinks that the goal is to obtain a transparent, deep red strip of plastic without the photosensitive silver salts on it. On a piece of negative film, a brightly exposed area will remain black while an unexposed area (like the perforated area at the edges) will be transparent after developing. While this produces a deep orange-ish filter, it seems to me that an exposed area will become opaque (at least to visible light).

There's an easy way to test this - shoot a few frames of brightly overexposed film and leave the remaining frames unexposed. Get it developed and try both the overexposed frames and the unexposed ones. If you get the results you're looking for with the "black" (exposed) frames, then you've proven that it does pass IR while remaining opaque to visible light.

Good luck and hane fun! What's the application, BTW?
 

BobVA

Enlightened
Joined
Aug 10, 2003
Messages
416
Location
North VA
I think the confusion is arising because some of the articles refer to slide (positive) film while others refer to print (negative) film.

You want the film to be black when developed, so negative film needs to be OVER-exposed and slide film needs to be UNDER-exposed.

If you get a roll of Ektachrome, just hand it right back for developing. If you get a roll of Kodacolor, strip it out of the cassette then roll it back in.

Have fun - let us know how it works out.

Cheers,
Bob
 

65535

Flashlight Enthusiast
Joined
Dec 13, 2006
Messages
3,320
Location
*Out There* (Irvine, CA)
Go buy a roll of Kodak 100 color film pay for it, go up to the photo counter open the film box grasp the canister and the leader and pull apart pull it until it is all out and there is resistance, then turn the winding post until it is wound up and give it the the person and say I want this developed and uncut.
 

finn

Newly Enlightened
Joined
Sep 8, 2007
Messages
56
Location
Germany
Thanks for the info.

...What's the application, BTW?
Handheld illuminator for use with GenIII NVGs.

I would like to build a high power handheld IR illuminator using an Osram Golden Dragon IR LED, and an inexpensive throw style flashlight body. I believe even the 950nm emitters emit visible light, which I need to keep to a minimum. I know I have seen people selling surefire heads, but I just don't want to pay that much for something I believe I can build.
 
Last edited:
Joined
Jul 15, 2007
Messages
590
Go buy a roll of Kodak 100 color film pay for it, go up to the photo counter open the film box grasp the canister and the leader and pull apart pull it until it is all out and there is resistance, then turn the winding post until it is wound up and give it the the person and say I want this developed and uncut.

Sheesh. Just go to the 1 hour place and ask them for some leaders. They cut off film at the front of the roll that's exposed when they attach it to the carrier that transports it thru the processor. There's at least 3" of waste film available for every roll.

And if you want a REAL IR filter, get this:
http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1918

Save some money- just ask for some film throw-outs.
 
Top