When using black and white infrared film the first and most important thing to remember is use a suitable filter, the film is highly responsive to light so you need to filter out everything except the red and infrared spectrum, this diagram shows the filter transmission ranges.



The minimum you need on the front of your lens should be a Wratten #25 or equivalent, this filter has a cut off range of 580nm, so you’ll end up with the red and infrared spectrum hitting the film.

As you can see, the greater strength of the filter the less red light and more IR light is passed through, right up to a Wratten #87C where no red/infrared light above 810nm is transmitted to the film. Black and white infrared film is sensitive to about 900Nm. With the strongest filter you will only get infrared and no more red light.

To give you an idea of how much light reaches the film, the pictures below demonstrate the different effects filters can have, the picture on the left used a Wratten #25 and the one on the right used a Wratten #87.

Using Kodak's HIE, you'll get a slip of paper inside the box with the details for exposure depending on which filter you choose to use. Its a fairly accurate guide for exposing the film.

To sumerise:

Using a Kodak Wratten #25 or equivalent, you should set meter at ISO 50, if metering through the lens (TTL) you should take your reading before placing the filter in front of the lens.

Using a Kodak Wratten #87 or equivalent, you should meter at ISO 25 and if you're using a Wratten #87C, you'll need to meter at ISO 10.

Bracket your shots by +/- 1/2 stop or +/- 1 stop, this should be more than adequate to give you some excellent results.

In case you haven't noticed on your lens, there's a little red dot, this is the infrared focusing mark, as infrared light focuses at a different point from the regular visable spectrum, so after you've focused, move the focal point to the red mark, not forgetting if you have an autofocus camera to switch that to manual.

You’ve seen the basic principle for black and white, now let’s look at colour infrared.