Infrared camera basic principal

http://en.wikipedia.org/wiki/Infrared_camera

It's been many decades since I did Infra imaging using special film available from Eastman Kodak. I purchased mine in the then popular 35mm roll format. I believe it was also available in 220 film, characteristically a 2-1/4 by 2-1/4 inch format but since I used 35mm exclusively for IR imaging, I can't be certain.

I'm also trying to remember if I used a special filter (red) to attenuate the energy from the visible spectrum but again, I think I did but it's been many years and I can't be certain.

Exposures aside, shooting with IR film was not much different than conventional visible spectrum film. The only difference I can recall was that one did not focus the same way.

Since the wavelength of IR is longer than visible light, the focal plane on which it is sharp was slightly different, further back inside the camera, as I recall.

Since there was no convenient way to alter the position of the focal plane, one focused using a red dot on the camera body instead of the conventional focusing marker next to it. This slight rotation of the lens moved the sharp image of the IR subject onto the image plane of the film.

I'm trying to recall if I used the same developing chemistry as with other B&W films, which is really what IR film was. It was NOT color film as some might suspect but rather a true black and white film that converted infra red temperature gradients into a conventional B&W grey-scale.

I suspect the IR film is still available. While digital imaging is obviously the dominant trend, some recon and intelligence cameras appear to be still using IR film because of the superior resolution. I got that info second hand so I can't verify it.

L.J.

I have tried the Kodak Infrared 35mm film about two years ago. As I recall I used filter that blocked out all of the visible wavelengths, so I had to focus without the filter, then correct the focus using some sort of rule of thumb (I don't remember how it was), then fit the filter and finally use VERY long exposures in order to get a 100% thermal image of the objects.

These films are not useful in thermography, their sensitivity only goes to 900nm and visible camera optics have limited infrared transmission.

The Kodak infrared film used these chemistries:

B&W: HC-110.

Color: E-4 or EA-5 chemistry.

See Kodak publication M28, CAT: 101 8364, Applied Infrared Photography

I used Kodak 35mm infrared film in a Pony camera with a Wratten 89B filter fifty years ago, just to see what it was about. There are issues with exposure times and focus. You should use as small an aperture as you can to increase your depth of field, or you may wind up with lots of fuzzy negatives. You should also experiment with the film before you start shooting pictures you want to keep, because the initial results can be very unpredictable.

In addition to the Wikipedia article recommended byTVP45, you might take a look at these:

http://www.vividlight.com/Articles/2915.htm

http://msp.rmit.edu.au/Article_03/02c.html

Processing your own film is a plus. Just keep developing temperatures low. Some of the images you get will be strikingly beautiful, and some will be disappointingly bland. You won't know what to expect until you do it. Good luck.

CR4 Admin: removed broken link.