[Leica] Exposure range of commercial film

[Gsam126 <Gsam126@aol.com>]

I've got a technical photography question which has escaped perusing a number
of book resources: What is the range of illumination, i.e., F stops, that
print/slide film can normally handle. I'm interested in this from the point of
view of landscape photography, where graduated neurtral density filters are
apparently used when, e.g., brightness of the sky may be far greater than
other parts of the frame, creating a situation where  one can only expose part
of the image correctly. I encountered this while attempting landscape photos
in the Himalaya, where, at alttitude, distant mountains where extremely bright
relative to foreground. To capture them, the foreground would be underexposed;
to get the foreground, the background would be overexposed to the point of
total loss of detail From reading, the solution is to use  the graded neutral
density filter. My question is , what is the exposure range (in F stops)
beyond which  such comopensation is necessary. Looking in Adam's classic tome
"the negative" and the more modern  take on the zone system in grave's book,
there is no discussion of this issue. What is discussed is the range of F
stops spanning zone 1 to 9 (10 stops). If the range of illumination in the
subject is greater (which could be figured out by taking spot readings of
darkest and lightest areas), the scene is considered to have increased
contrast, and the film (B&W) can then be developed to expand its range of
useful contrast. However, there must clearly be a limit to the degree of
useful expansion. (This is also of limited use with color film). I have been
unable to find any written discussion of the exposure range for the commonly
available Kodak/Fuji films. Knowledge of this would be essential for outdoor
photography: to enable the photographer  to know when a given image would
require a graded neurtal density filter. Also, can pre-exposure be used to
solve the same problem? Vis a vis the G1/G2, has anyone come up with work-
arounds for the difficulty (?impossibility) of using graduated neurtral
density filters? 
I would appreciate some help. Thanks Greg Ruskin