There is a lot about Print Studio Pro that I don't understand yet. I suppose that's because I haven't completely integrated it into my workflow. When I have used the Pro mode, I have simply open an image from Lightroom and selected that mode and printed. You may or may not be aware that Lightroom functions primarily in the ProPhoto RGB color space. I read the same description that you did, and was curious about that. But I just chose the Pro mode in PSP and let it print. Close examination (with my eye, not scientific) shows that the print was just slightly lighter than the one printed using the ICC profile. That's the only observation I've been able to make so far. I haven't really drawn any conclusions. Anyone who wants to know more about this can find answers by doing their own printing experiments.