It depends on the meter. I found that my meters worked better at EI 400 when metering through the filter.
HIE will have some base fog by now, though, even if frozen so you might need to use a lower EI and compensate in the processing.
Jim MacKenzie - Regina, Saskatchewan, Canada
A bunch of Nikons; Feds, Zorkis and a Kiev; Pentax 67-II (inherited from my deceased father-in-law); Bronica SQ-A; and a nice Shen Hao 4x5 field camera with 3 decent lenses that needs to be taken outside more. Oh, and as of mid-2012, one of those bodies we don't talk about here.
I'm a fan of f/11 and 125th. Good depth and a full stop more exposure in the shadows. Remember, your highlights will get all the exposure they need. Its the shadows that will need the extra exposure from a dark filter on the front.
I rate it at 680 iso using a 25 red filter I then bracket two thirds of a stop either side of it. I set my aperture at f16 and spot meter with my camera (OM4Ti). My lens of choice is the 24 mm so no problem with DOF. I develop it in ID11 (1+1) for 13 mins. All 3 negs are printable I just pick the easy one. Check out my recent IR work especially my work taken in Northern Ireland.
Thanks to all of you... however I didn't get any of the answers before I had to leave. I googled the question and came up with 400 - then when I got there I didn't find my doggone filters till I was leaving! My son had put the bag in the trunk and I thought he'd not put it in the car at all. I shot a few frames just for the heck of it. Ha. Oh well. Next time I'll be ready.
Unless you have large quantities of HIE to spare, I'd try and obtain and read Laurie White's book or better still Hugh Milsom's " Infra-Red Photography -A Complete Workshop Guide." HIE is getting a bit precious to waste.