Shooting IR outdoors w/strobes, what kind of exp should I use?

I'm shooting some outdoor portrait shots with Maco IR film.<br>

At ISO 100 without the IR filter, I can get some nice exposures

shooting f5.6 at 1/500th. That's a meter reading of the sky at

1/250th/5.6 minus an f-stop to make it 1/500/5.6. (I do this to

darken the sky while leaving the subject normally lit)<br>

With the IR filter in place, I get a reading of 1/4th/2.8. Minus an

f-stop, that makes it 1/8th/2.8.<br><br>

Should I be shooting at 1/8th at f2.8 or should I raise the shutter

or f-stop because of the strobe light?

You should always add light levels. Sun + strobe = new light level.

However, since you are using IR, and nothing really meters for IR, you should do this by experimentation. What the IR filter does is cut off light in the visible spectrum and let the near-IR through. If this was Kodak film, I would say pretend you are shooting ASA400 with no filter on the camera, and meter for that (using a hand-held meter, though).

Since you are using Macophot, I recommend that you ignore what in-camera meters tell you, use an external meter, and make test shots with bracketing and different strobe positions. All of the IR films have somewhat different response curves, so in the IR spectrum I can't tell you what will happen.

Just go ahead an burn some film and find a good answer. That's the best way to go about it.