Velvia 100F and Velvia 100 are two different films, I myself don't like Velvia 100F, the depth and saturation is not there as it is with the ISO 50, but people I know in Japan where the 100 has been available have stated the non-'F' Emulsion is very close to the 50 and if you shoot at 80 and process normally you will see the same depth and color saturation as 50 shot at 50. But I know a great many of us that shoot 50 at 40 and process normally.