The lenses will be the same focal length. They just won't have the same
field of view as you remember.

Your lenses project a circular image at a set distance from the rear of the
lens. You can see this by holding the lens between a light and a piece of
paper. It projects this image onto your piece of film or digital sensor. The
circle is designed to cover an area 36x24mm- i.e., a frame of 35mm film. The
sensor in a digital camera is smaller than this. The effect is that the
lens, when used on a digital body, gives a field of view approximate to that
of one 1.5x the focal length on a 35mm body. The focal length, however, is
unchanged- the depth of field remains the same at a given aperture, for
example.

As it is, then, a shorter focal length lens is needed if you want something
that equates to a 24mm- effectively, a 16mm lens. A 16mm wideangle for a
35mm camera would be rather heavier than your 24mm lens. Mercifully, a 16mm
lens designed specifically for smaller format (digital) would not need to be
as big as one designed for 35mm- probably no different in size or weight to
a 24mm lens for 35mm. The practical problem is there is no fixed 16mm
digital lens for Nikon. The closest you'd get is one of the zooms
encompassing this range.

Martin

So if you want to sell lenses I might be interested, but I would keep them
and just make the conversion.

Girlfriend has N80 and I have D70s, we want a lens we can share like a
70-200 or the 80-400, however on my camera, I will end up with 300 or 600 on
my end, which is ok, but overkill, unless I am a couple of miles from my
subject (joke).  The 200 lenses is the superior because of the silent wave
motor, but the rest is comparable.

I still don't know how we will work this out, because one lens will suffice
for both cameras, and one day I will hand off my D70s to her and get a
better one, so hopefully the lenses will still carry over, so we don't have
to purchase more.

Later.

Monty

Welcome to the mine-field!  People get themselves and others confused
all the time on this issue.

The actual focal length of a lense is a matter of basic physics.  It's
fixed, it doesn't change.  

If you cut the center section out of a 35mm negative and enlarge just
that part, you'll get a narrower angle of view than if you'd enlarged
the entire negative.  I'll *look* like you shot it with a longer focal
length lens (although you may, depending on the degree of cropping,
notice increased grain if you do this with film in the real world).

Digital SLRs, except a couple of top-end models by Canon and a
mid-level model by Kodak, have digital sensors smaller than a frame of
35mm film.  Consumer digicams have *much* smaller sensors than a frame
of 35mm film.  

LOTS of people have spent enough time working with 35mm SLRs that they
have a deeply-rooted idea of what angle of view they'll get with a
lens of a given focal length *on a 35mm camera*.

By the usual processes of cultural evolution (i.e. random thrashing
around until something ugly that works much of the time is dominant),
it's become standard for consumer P&S digicams to give the
35mm-equivalent focal length for lenses.  Since the different cameras
have different sensor sizes, this is useful for comparing two of those
cameras on an even basis, as well as for giving people familiar with
35mm lenses an idea of what the field of view will be.  

People talk about the "focal-length multiplier" for digital SLRs --
the Nikon models have a 1.5x multiplier, so your 50mm lens gives the
same angle of view you'd get on a 35mm film camera with a 75mm lens.
Some people will object strongly to the term "focal-length
multiplier", and they're technically right, so to shut them up I often
call it a "crop factor" instead.

Why does it matter?  Doesn't all *that* much.  But when calculating
depth of field, or bellows extension, you need to use the *real*
physical focal length of the lens, not any of the other numbers that
get thrown around.  And many of us get hives when we see people
misunderstanding things, even when the misunderstanding makes no
difference to what most photographers do day-to-day.  Call us anal if
you like :-).

Wouldn't you rather wait for the Nikon D200?

- Siddhartha