Kodak High-speed Infrared

I've received enough questions about this film that I've decided that it's worth writing down a few notes to share with people.

Kodak high-speed IR comes in two sizes: 35mm and 4x5 sheets. The 35mm is easier to work with, cheaper, and has a more pronounced grain which is one of the things that make this film so distinctive. A good example of this grain is the stump image [big].

The 4x5 sheet film, like any other large-format film, gives you a much richer depth of intensity, and much finer grain. The water temple image is a good example of this. [big]

There are other manufacturers of infrared film, most notably Konica, but these other films do not see as far into the IR as Kodak and I've never tried them.

Handling

Infrared light has longer wavelengths than visible light, which gives it the ability to bend around corners more ("diffraction"). This is what gives IR film some of it's more striking effects, but it also causes some problems. IR light can get through the felt light baffle in film canisters and fog the film during handling. It can also pass through some kinds of cloth and plastic. For this reason, you must take the following precautions:
Not all cameras work
Cameras with plastic bodies may allow IR light to reach the film. As far as I know there's no list of which cameras do this, so you'll just have to find out the hard way. Metal-body cameras work fine. I've never had any trouble with my Minolta SRT 201, Minolta XG-M or Minolta X-700.
Load film in a darkroom.
You need to keep the film canister out of the light at all times.
Changing bags don't work very well.
I've used them when nothing else was available, but you can see the fogging in the flim leader afterwards. Luckily, the combination of changing bag and felt baffles protected the film well enough, if not perfectly.

Exposing

Kodak high-speed IR is a little tricky to expose right. The film sees a band of light that neither your eye nor the light meter can see, so it's difficult to know how to expose it and any attempt to just select a meter setting would be in vain.

Anyway, with all that ambiguity, I have a rule of thumb that works pretty well for me: In the cool light of the evening and morning, treat the film as ASA 25. In the warm light of the mid-day, treat the film as ASA 100. In the hot light of an incandescent bulb, treat the film as ASA 400.

The best thing you can do is bracket your exposures a lot. In fact, the "stump" picture actually came from my first test roll when I was trying to determine the exposure to use. You should bracket every exposure +/- one and two stops (for a total of five exposures) if you can.

The other reason to bracket is that different exposures will cause different effects on the film. One exposure may give you a sharper image or more pronounced grain, while a longer exposure may give you more of that "glowing" effect. A good example of this is the trees in the forest photo in which the long exposure brought out the detail in the tree trunks in the foreground while causing the glowing effect in the background.

(BTW, the glowing effect isn't entirely from the infrared light, but from the fact that the film has no "anti-halation" backing. That's an opaque backing on regular film that stops the light that makes it through the emulsion and keeps it from bouncing off the back of the film. Kodak IR has no anti-halation backing and so the light bounces back and forth inside the thickness of the film, causing the highlights to diffuse.

(Of course, some of the effect comes from IR's long wavelength which causes it to "bend" around obstacles that short wavelengths can't pass. That's why the felt light trap in the film cans don't work very well and you have to load the film in a dark room. Black changing bags don't work perfectly either -- you'll be able to see the film leader has been fogged if you change film in a changing bag.

Above all, EXPERIMENT! This is a very difficult film to predict, but the surprises are usually pleasant.

Processing

This is the easy part. Just develop normally in D-76 according to the directions. Just remember to keep the film away from light when loading it into developing cans. Don't use changing bags. To be on the safe side, I use metal developing cans.

Good luck and have fun.

--ed falk