Astia 100F provides neutral colors and relatively low contrast. Velvia 100 is arguably a 100 speed version of Velvia 50, albeit with some differences in color palette, reciprocity and possibly contrast; it is a high contrast, super saturated film. Velvia 100F falls between Provia and Velvia in terms of color saturation and contrast; it was originally intended to replace Velvia 50 but was not saturated enough to fulfill that role.
Do a search for these films here of the LF forum and you'll find lot of discussions about them. The APUG forums are also a good place for additional information.
Ken Rockwell is controversial but his opinions on the various Velvias are listed here:
http://www.kenrockwell.com/fuji/velvia100.htm
http://www.kenrockwell.com/tech/velvia100f.htm
Bookmarks