For the sake of experimentation and maybe getting some novel, interesting results out of it; is there any colour film out there that has especially good spectral sensitivity? Sensitive beyond the visible spectrum, with which I could use a 590nm IR-pass filter? I love the look of 590nm, but I don't love the cost of converting a digital camera, nor digital images, nor the cost of IR color films. I understand exposure times would be considerably longer, but is this even worth exploring? Taking a quick look at Portra 400 charts, there seems to be some sensitivity for magenta and cyan dyes at 590nm, if I understand correctly.

If anyone has prior experience with such a thing, or can offer insight, that'd be greatly appreciated!