[Leica] f/1 and others, was should i buy a hockey puck?

[Malcolm McCullough <MM4@mm-croy.mottmac.com>]

Curious Dan Honemann asked, quite rightly:

<<Okay, math whizkids, how comes it that Leica (and Canon) can make an f1 
50mm
lens, but no one can make an f1 wide angle lens?  I should think it would
get progressively easier (and smaller) to make an f1 35, or 28, or 24.  But
you get down to 24 and the fastest lens you can find is the Canon EF
24/1.4L.  How come?>>

and later

<<P.S. I'm still waiting for the mysterious answer to why no one makes a 
28mm
f1.0 lens.  And I'm hell bent on posting inane messages like this till I get
one!
Just a threat, not a promise.>>

Well I'm not going to claim to be a maths whiz or even a kid, but I'll offer 
an answer.
It is relatively easy to produce short focal length lenses of very wide 
apertures, but the problem is producing them with wide angles of coverage. I 
have a Kern  f0.9 13 mm lens, an Angenieux f0.95 25 mm lens and an Ang. f1.1 
16 to 44 mm zoom, but they are movie lenses and don't cover a 35 mm frame. 
There are microsope objectives with very short (by 35 mm still camera lens 
standards) focal lengths and much wider apertures but they don't have a wide 
field of view.

The problem with the wide angle of coverage is with the size of the front 
elements. The Canon 24 mm f1.4 has a huge front element in comparison to the 
Angenieux 25 mm f0.95. (I bought a T90 just so I could use that Canon lens, 
BTW). Far and away the biggest lump of glass I have in a prime lens is a 5.7 
mm f1.6 Kinoptic that only covers the Super 16 format (with a soft, woolly, 
huggy sort of glow). These comparisons are affected by the degree of 
retrofocus in the designs, BTW.

On a similar subject: Angenieux and Zeiss have got together to produce a 
neat behind-the-lens converter to use movie lenses on video cameras with 
smaller chips. The device maintains the original angle of view by reducing 
the focal length (the image circle becomes smaller). Because the apparent 
aperture remains the same physical size, the f number goes down. Exactly the 
oppposite of a behind-the-lens tele converter.

And while I am on this fascinating subject, here is a list of f-stops in 
thirds from 0.5 to 1.4, to three sig. figs:

0.500
0.561
0.630
0.707
0.794
0.891
1.00
1.12
1.26
1.41

and in halves:
0.500
0.595
0.707
0.841
1.00
1.19
1.41

I was once asked for quarter stops by another DP who wanted to give his 
clients the impression that he was extra accurate. I argued that it was just 
an illusion of accuracy (which I wont explain here - this is long enough 
already. A pox on meters with readouts in tenth stops). Maybe we should get 
LUG Persnickerty Special Edition Lens Sets with tenth stop detents so we can 
be 'impressively' accurate, and then we should go for a Just Connect Special 
Edition Lens Set with no aperture markings or detents whatsoever.

Regards,
Tenth-Stop McCullough, The Most Prexactest DP. 
Yeah, just move it off wide open a touch, that should do.