f/1 is impossible with a Nikon F-mount due to constraints imposed by
the inside diameter of the mount flange and its distance from the image
plane.  The Canon EOS mount has a larger diameter and a shorter flange
distance, which is why lenses like the now extinct 50/1 are possible.
Its also the reason that so many lenses can be adapted to the EOS
mount.

In practice it may not make sense to use f/1 lenses with electronic
sensors.  The problem is that the marginal ray angle of an f/1 beam is
30 degrees, which exceeds the acceptance angle of any sensor I know of.
The effect would be that your f/1 lens will be "stopped down" by the
sensor so that it will not actually function as an f/1 lens.  Note that
this problem will occur on-axis as well as off-axis, and has nothing to
do with the ray angle problems caused by a short exit pupil distance.
I suspect this problem is one of the reasons Canon decided to drop its
50mm f/1 lens.

In lens design terms, I would expect the two shorter lenses in your
list would be larger and heavier than their FF equivalents because of
the stuff you have to do to deal with the large working distance.  An
f/1 reverse telephoto lens is certainly possible, but its going to be
big.  On the other hand, its reasonable to expect a 60mm/1.0 DX lens to
be about the same size as an 85mm/1.4 FF lens.

Brian

I replied already to the original thread. However, since I guess this
may have picked up new readers, here is a paste:

XXX

Of course they would be possible; I can't imagine why Jeremy should
think otherwise. Merely scaling down the design of a 50mm f/1.0 by 0.7
would give something close to a 35mm f/1.0 capable of covering APS-C.
Cine cameras used to have very wide aperture zooms (often with a big
zoom range as well) and f/1.0 lenses were not uncommon. Certainly Zeiss
used to make a 24mm f/1.0 cine lens many years ago. It may be so with
camcorders, I never really looked at them in detail.

Whether it would be desirable is of course another question. Clearly,
the smaller the format the easier it is to get the thing (necessarily
*much* larger than an f/1.4, to avoid vignetting) into a package of
manageable size.

XXX

Since writing this, an afterthought: it seems that what is difficult is
to make an f/1.0 lens with an angle of view much larger than a
"standard" (46 degrees on the diagonal). If you go too much wider than
this, vignetting becomes too difficult to control.

David

If you can find one Canon made a 50mm f0.95 lens for their rangefinder
in the 60's. BUT the quality of the lens wasn't good enough to
compensate for the cost. You can buy cine lenses as already been said,
but I once looked at a 16mm Zeiss t1.0, it was thousands of $. Lens
design is part science, art and marketing. If they can only sell a few
lenses the costs will be unafordable. It seems most folks with digital
SLRs are content with slower, cheap optics.

Tom

Given the specs common in 16mm and 8mm motion picture lenses and my
understanding of the underlying constraints, they should be able to do
this, and I wish the bastiches would get off their duffs and *do* it.
It's one of the strongest argument for small-sensor cameras.