The results are in. I loaded 25 holders, one side w/ Velvia "Classic," the other w/ 100F, and shot duplicates of all scenes, changing only the shutter speed. (I would post images, but not sure my inadequate scanning ability would suffice, so words will have to do for now.) Here are my initial thoughts, fwiw: 1) It appears that there is actually slightly more than one stop difference between 50 & 100F. Probably should've changed exposure by 1 1/3 stops instead of just one. This warrants further testing. However, the difference is slight enough that it does not alter my opinions. 2) If you were hoping for a 100-speed Velvia with the same color pallette as 50iso, you'll be disappointed. I'm underwhelmed in most situations. The color of 50iso is noticeably warmer, meaning that those nice, brilliant alpenglow sunrises look more vibrant with 50. The 100F is much flatter. 3) In overcast light, the 100F looks quite good, rendering a more accurate, but still nice color. Parry's primrose that I shot alongside a stream looked much more true to life than 50iso. Greens looked more blue-green, as they were in real life, than the warm green of the 50. 4) Shadow detail was a bit better on the 100F. On some shots using a graduated ND filter, the transition was less evident due to the increased detail where the transition of the filter came into contact with shadows. 5) As far as grain goes, my unscientific eye could detect absolutely no difference between the two. Both Velvia classic and 100F show amazingly fine grain in large swaths of empty blue sky. Pretty impressive for a 100-speed film. Conclusion) I was really hoping for a 100-speed replacement for Velvia classic, as I don't want to carry multiple types of film in the field. For 10 years Velvia has been my film of choice, an emulsion that, for my taste anyway, always did what I wanted it to. Overall, 100F is a disappointment. Shadow detail is nice, but when I look at a photo, I want to be impacted by the whole of the photograph, and in that I found the "oomph!" of 100F lacking. If you plan to shoot anything with red, yellow or orange hues in it, skip the 100F. Interesting when one considers that many times, when Fuji was releasing a new version of Provia, rumors had it that it was actually a stealthy way to release a 100-speed version of Velvia, while in truth it was just a much less saturated film. Finally, after over a decade of producing THE film for landscape photographers, Fuji releases an actual 100-speed version of Velvia, a film that looks notably different (and not in a good way) from its successful predecessor. What were they thinking?