Probably nothing, if you truly focused on the same object both
times.  They are simply two different ways to accomplish the same thing.
Normally, I would go by the point to subject which I want in sharp focus
and let it autofocus at half depression of the shutter relase, and then
shift for desired framing.  However, If I had the camera on a tripod,
or were in a situation where the actual framing was likely to remain
fairly constant for a series of shots, and the subject of prime interest
was away from the center of the frame all of the time, I would probably
shift the focus area to cover that, so I would not have to constantly
re-frame.  (An example might be two people in a debate, or a tennis
game.  Or even two cats in a face-off.)

    The D70 simply offers you multiple ways to accomplish most
tasks, so you can select the one which best fits the situation and your
working habits.

    Yes.  It will probably be some time before the language adjusts
to the change in the hardware. :-)

    The field of coverage of that lens on the D70 is equivalent to
lenses covering the range 27mm to 105mm on a full frame camera.  Some
other features, such as apparent depth of field, are functions of many
things, including the *actual* focal length, and the magnification to get
the final print.

    Yes.

    The term "35mm camera" refers to a dimension which does not even
*exist* on the D70.  It is the width of the film such a camera uses,
including the sprocket holes.  The actual area of film exposed in a
*full frame* 35mm camera is 24x36mm.  In a half-frame 35mm camera (same
size film, but a smaller image), the image area is 24x18mm (image is now
taller than it is wide with the camrea body horizontal).  The "wide
angle" and "telephoto" definitions are for a full-frame 35mm camera, not
for a half-frame one.

    You mean the wide angle or telephoto definition?  It is a
function of the size of the image (the sensor in the digital cameras, or
the exposed area of the film in a film camera), and the actual focal
length of the lens.  A lens which would be a "normal" on the D70 would
be a mild telephoto on a half-frame 35mm camera, and a mild wide angle
on a full-frame 35mm camera.

    And the actual definition is a function of the visual effect of
an 8x10" print viewed at a standard distance.  A "normal" lens will give
a perspective like viewing a scene through an 8x10" window at the same
distance.

    You select wide angle or telephoto lenses either to allow you to
get what you want to photograph into the frame at a distance which you
can realistically achieve (e.g. a wide angle may be needed to cover a
given scene indoors, when you cannot back through a wall to get more
coverage), or a telephoto may be needed because there is a gap between
you and what you are photographing (e.g. from one rooftop to another)
and you cannot get closer to what you want to photography.

    *Or* -- you may select them because of the different perspective
they give to the image.  Longer telephotos tend to collapse apparent
distance, while wider wide angles tend to exaggerate it -- such as a
photograph of a face in which the nose may predominate.

    Take your lens and camera and start taking photos, and note the
effects.  Pick some scene outdoors, and back away to the maximum
distance at which you can fill the frame using the lens zoomed to the
maximum.  Take that photo.  It does not matter whether it is anything
particularly interesting in its own right, as it will cost you
effectively nothing, unlike with film.  Now, zoom to as wide a setting
as you can, and walk forward until you get the same scene filling the
frame.  Take that photograph as well.

    Now -- go home, and either put them on the screen, side by side,
or print them both to the same size.  Spend some time studying the, and
note how they differ.  Pay attention to the objects in the background.
Pay attention to things near the center of the frame.  *See* what the
choice of focal length does to the image.  Even longer or wider lenses
do this even more, but you have enough to get an idea what it does.

    Enjoy,
        DoN.

I think what's going on here is that many photographers need something to
compare the new digital equipment to, especially DSLR cameras.  So, the
comparisons get made to a 35mm camera.  I know, without even seeing it, what
I will see if I put a 50mm lens on a 35mm film camera.  So, when I read that
a 50mm lens will appear to be a 75mm lens on a D70, I have a pretty good
idea of what I will get without even trying it, due to prior experience.

I'm sure this will all change over time as digital replaces film.  It's a
lot like where many of today's kids only know that music comes on CD's.
Vinyl or tape is very old history to them.

Still, I predict that film will still have a place, especially in the art
world, and that the goal of many digital camera manufacturers is to make an
image sensor the same size as a 35mm frame.  This would eliminate much of
the confusion over focal length, and bring things back to a "standard."

Now, this may or may not happen, but I think it will.  The next step will be
"medium format" digital, and so on and so on.  Remember, if you are still
using film, you have to make these focal length conversion if you use large
or medium format cameras.  A 50mm lens will not be the same on a 35mm, as
compared to a 2 1/4, as compared to a 4x5, as compared to an 8x10 format
camera.  As the image surface gets larger the lens gets "wider," by
comparison.  So, it just makes sense that if the image gets smaller, like
the example of the half-frame camera, the lens would appear to be longer.

Again, just go out and have fun.  Take a lot of photos and compare them to
see what you get.  Take portraits with the camera set at wide angle and with
the camera set at telephoto.  See what you get.  There are some specific
rules in photography, but if you want to get artsy, rules are meant to be
broken.

    Actually -- it is still there.  If you read it once, it would be
marked as already read, and not normally presented to you a second time,
depending on just how your newsreader program is set up.

    And I typed a long reply to that one, so check back.

    Enjoy,
        DoN.

When would you want to set the exposure for a part of the image
that you didn't want (also) in focus?   It's hard for me to imagine
images where you want exposure set on one thing, and focus set on
another.

I think it was the AE/AF lock button that I changed the behavior on.
Anyways, figure out these two & the problem is solved.