You may want to start out at 50 with a 25 red or 29 red filter and bracket some. Before you raced out the door I hope you loaded the film in complete darkness.
If I meter through the filter, I set the ASA at 200. What works in bright sun is usually f16 at 1/125. Both were gotten from Laurie White's book on IR and both have worked for me in the past.
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.
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.