No - cm.  A 6x6 frame is approximately 6cm x 6cm.

The x in 21x magnification (not zoom - it isn't a zoom lens!) means
it magnifies by 21 times compared to a "normal" lens.  That, of course,
depends on just what you consider a normal lens to be.  In this case
they obviously are assuming an 80mm lens as normal (on the Hasselblad).
While that's close to the diagonal of the frame size (one criterion
for choosing a "normal" focal length) many people would consider this
to be a fairly wide normal lens - it roughly corresponds to a 43mm
focal length on a 35mm camera, not the 50mm most people think of as
normal (which would be equivalent to a 100mm focal length on the
MF body).  But assuming 100mm as the normal lens on the Hasselblad
would only let them call it a 17x magnification - not as impressive.

Surely the "x" means "times" and is the ratio of focal lengths at the
extreme ends of the zoom range. This will be independent of any camera or
other lens and not relative to anything else in the universe.

Mike.

Very interesting...

I wonder what it would be for my Sony Mavica with the CrystalVue LX8
scope attached to it?  The Sony has a 2x digital zoom and a 3x optical
zoom and the CrystalVue LX8 has a 8x optical zoom.  With all of this
magnification, I am surprised that I can still take long distance shots
without a tripod and they come out perfectly focused and sharp.

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Except that 35mm film is 35.0mm x 23.3mm, which is a diagonal of
42.05mm, hence that focal length gives 1x magnification.

Therefore a 50mm lense would give 1.19x magnification, using
35mm film.

Regardless, the idea of "35mm being the standard camera lens" is
false.  If that 1700mm lense were mounted on a 35mm camera, the
magnification would be 1700 / 42.05, or 40.42x.

For 6cm x 6cm film (which is what it was made for), the diagonal
is 84.9mm (1x magnification), hence 20x magnification.

Note that the diagonal distance for 35mm film is almost exactly
half that of 6x6 film, which indeed means the magnification is
twice as much.

On a Nikon DSLR, with a sensor that is 23.7mm x 15.6mm, a
"normal" lense for 1x magnification is 28.37mm.  A 1700mm lense
would have a magnification of 60.

I don't see that as such a big deal in itself, as I was using an
800mm f/5.6 lense earlier today.  With a 2x telextender that
provides 56x magnification, and without it the magnification is
28x, which is significantly more than the 20x that 1700mm lense
gets on the Hassy.  Of course...  an f/4 lense that gets 20x on
6x6 film is somewhat more impressive in virtuall *all* other
ways than simple "magnification" compared to a 12 megapixel
digital image!  :-)