Scanning is a black art. There's a LOT to learn, and I've found myself
re-scanning stuff when I see what my old scans look like :-).
For old, relatively large B&W negatives (sheet film, 120 roll film), you
can get quite decent results with a good flatbed scanner -- currently I
use an Epson V700. The V750 even supports fluid mounting, which
unfortunately makes a considerable difference if you're going for
top-quality results ("unfortunate" because it's extra cost and effort, and
some extra risk to the original). You won't be getting everything
possible out of the negative most likely, though.
For 35mm film, I do not find the V700 at all satisfactory. It doesn't
hold the film flat enough, for one thing. For this kind of very small
film (I've scanned a bunch of 110, too, which is even smaller) a dedicated
film scanner is significantly better.
Both flatbeds and film scanners are quite slow.
Almost anything will do for reflective (as opposed to transparent)
originals; there's just not that much brightness range there.
I haven't worked with larger originals. Larger flatbeds exist, and are
priced accordingly :-( .
I've been happy enough with the Nikon software on their Coolscan scanners
(all discontinued now; but "old new stock" is still available, and used
units are available).
Remember, resolution is very rarely the thing a scanner is lacking. So
don't be impressed by high resolution numbers.
