You cannot make exact meter readings to determine exposure for infrared films.
Exposure meters are not calibrated for infrared radiation, and the ratio of infrared to visible radiation varies with the light source.
Make trial or bracketing exposures over a five-stop range to determine the proper exposure for your application.
Under average conditions, use the following speed ratings to make starting-point exposures with handheld meters or through-the-lens light meters.
For through-the-lens camera meters, make your readings before mounting the filter over the lens. Then ignore the meter reading/readout after attaching the filter.
