Many long-term users of Velvia 50 point out that Velvia 100F has a much more enlivened palette and better contrast, though greens are more subdued than the 50 stablemate. It picks up yellows which is an advantage to me, as a rainforest photographer, because it brings up the nuances of mosses, fungi and lichen where Velvia 50 would miss. 100F also has exceptionally clean whites and blue, particularly evident when photographing snow and sky scenes. There is an oddball brother in the stable: Velvia 100 is an entirely different beast with an extremely enriched palette and, from my own experiments, does not hold highlights anywhere near as well as 50 or 100F. Having said that, individuals need to experiment copiously to determine which of these three films suit their own task at hand; no one Velvia film will do for all conditions. Recent Velvia 100 tests did not please me at all. I've printed RVP 50 and 100F trannies to Ilfochrome jobbing and they have both produce outstanding results, but from long experience, I think RVP 50 can still be considered the gold standard.