It's not so "new" anymore, but I'm talking about the only kind kodak currently makes (the latest version that they started making after discontinuing the NC/VC films). While I intend on doing my own tests, I'm curious to hear what your tests with Portra 160 4x5 have shown the film's native ISO to be. Also, if you'd care to share your test technique/scene you chose to conduct the test on, I would be very interested. With 35mm Portra 160, I usually rate it at ISO 50, or even slower if the contrast of the scene is low. I am often shooting naturally lit interiors with a substantial contrast range. I have gotten a few 4x5 shots developed, and from what I've seen, the 4x5 Portra has just as much if not more highlight range than 35mm Portra. I have access to a color darkroom at my school, as well as Imacon scanners, so I have plenty of good printing tools to test with.