>After playing with the 25-50 I decided I wanted something a little wider.
>Thinking that the 20mm is a little too close to the 25mm end of the 25-50
>I decided to look for an 18mm.
--Makes sense. I had a 24mm and an 18mm. When I bought the 20mm, I stopped --using the 24 and sold it, same with the 18. The 24 and 20 were close, but not --as close as the 18 and 20 (but not different enough to ever carry both).
--Maybe the 18mm does make sense for you if you keep the zoom, though compare --the 20 and 18 before buying, if possible - their coverage angles are VERY --close.
>What specifically causes you to prefer the 20 over the 18?
--The 20mm f2.8 is a very wonderful lens optically - somewhat better than either
--the 18mm f3.5 or 24mm f2.8 (and an additional notch ahead of the 25-50 at
--25mm [I have owned several 20's and 25-50's]), and far ahead of the 18mm f4
--(one of Nikon's few poor lenses). The 18mm f3.5 is excellent in color by f5.6,
--though it improves through f11 or so. It shows considerable light fall-off
--at wider apertures (until about f8 - unusual for Nikkors). In B&W, it is very --noticeably inferior to the 20mm f2.8 (avoid the other Nikkor 20's).
--Hope this helps. David Ruether