filmscanners: Scanner Focus

[HMSDOC@aol.com]

I am an amateur photographer who is rather new at the whole scanning process 
and have been lurking for a few weeks and appreciating the education.  
Finally, made the jump and bought a Canon FS4000 which arrived 2 or 3 days 
ago.  I have 2 questions which I hope are not too basic for the group.

The first has to do with focus.  Every review I have read has commented on 
the sharpness of this scanner, and though I have read of dissatisfaction and 
poor results with some other aspects of the scanner, I have never read of 
anyone having problems with sharpness/focus.  So I was a bit surprised when, 
to my eyes, the scans appear a bit soft.  I am starting out with sharp slides 
or negatives with a tripod mounted Canon Elan 7 and good quality Canon prime 
lenses and images that look sharp on a light table with a 4x loupe.  The 
films are either Fuji Velvia or Provia for slides and Fuji NPS or NPC 1660 
for negatives. The auto focus is on, and the scans are at either 2000 or 
4000dpi.  With unsharp mask used to sharpen the image in my image editor the 
situation improves significantly.  But how does one tell if there is a 
problem with the scanner focusing mechanism?  If you take the scanner off 
auto focus you would have to scan at each of lots of different possible focus 
settings to compare to the original image.  I did try scanning at the two 
extremes of the manual focus setting and the images appeared a bit worse than 
on auto.  I guess my question here is how to know if the scanner is focusing 
properly and am I confusing the concept of focus and sharpness?

The second question has to do with background noise in dark areas.  I have 
some slides with dark backgrounds from either flowers taken against black 
backdrops or butterflies taken with a flash that illuminate the butterfly 
well but leave the backgrounds dark.  When scanning and viewing in my image 
editor I can see a moderate amount of shadow noise...but what is 'good' or 
'normal'.  If I keep zooming in and blowing up the image it obviously becomes 
more prominent, but at what point does it become poor performance or a 
problem with the scanner.

Thanks for any help.

Howard
HMSDOC@aol.com