If you go to f.01 assuming it is mathematically possible would you have ANY dof? Or just a very soft crappy image. (for the first question assume that it is very sharp.)

auto will destroy us all

a little off the topic, I have read both sides comments and it kinda makes me doubt if the 25 0.95 really beats the 25 1.4 in sharpness under the same aperture.

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http://www.flickr.com/photos/jyc860923/
Panasonic DMC-GF3
Olympus PEN E-PL5
Panasonic Leica Summilux DG 25mm f/1.4
Lumix G Vario 14-45mm f/3.5-5.6 ASPH/MEGA O.I.S.
Lumix G Vario 45-200mm f/4-5.6 MEGA O.I.S.
Lumix G 14mm f/2.5 ASPH
M.Zuiko Digital 14-42mm f3.5-5.6 II
mecablitz 44 AF-1 digital

Curious why you thought this comment should be posted in this thread?

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At first blush I am tempted to conclude that a satisfactory hobby must be in large degree useless, inefficient, laborious, or irrelevant. - Aldo Leopold

GH2 + Lumix 7-14/f4 + m.ZD 12/f2 + Nokton 25/f0.95 + m.ZD 45/f1.8 + SMC-M 50/f1.4 + m.ZD 75/f1.8
Flickr
Hiking blog

The aperture limit for a lens is about f/0.7. You can use the usual DOF equations to see how much (or how little) depth of field that aperture gives.

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Cub
Panasonic G3, 14-45mm, 20mm, 45-200mm, Olympus E-PL1, 9-18mm, 45mm

Wikipedia has a neat summary of the fastest lenses ever made:
Lens speed - Wikipedia, the free encyclopedia

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Olympus E-M5, Sony A65, lenses.

Why is that? I'm genuinely curious

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At first blush I am tempted to conclude that a satisfactory hobby must be in large degree useless, inefficient, laborious, or irrelevant. - Aldo Leopold

GH2 + Lumix 7-14/f4 + m.ZD 12/f2 + Nokton 25/f0.95 + m.ZD 45/f1.8 + SMC-M 50/f1.4 + m.ZD 75/f1.8
Flickr
Hiking blog

Thanks for starting this thread. I was thinking about this all afternoon after reading the articles on Stanley Kubrick's "Barry Lyndon" in this thread earlier:

Stanley Kubrick - Photographer?

That list on Wikipedia has me wanting to see some of these bizarre lenses, such as the f0.5:

USSRPhoto.com - Russian / Soviet Cameras Wiki Catalog - World's fastest lens

There are some photographs taken with the Rayxar 50mm f0.7 on an EP-1 here:

Hand mit Rayxar 50mm f0,75 | Flickr - Photo Sharing!

As the original post suggested: mush!

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Panasonic G1 and GH2; 20mm f1.7; Leica Elmarit 45mm f2.8 Macro; Olympus 12mm f2; Nokton 50mm f1.1; Nokton 25mm f0.95; Samyang 7.5mm f3.5; Complete set of Pentax Auto 110 lenses and adaptor; large collection of Minolta MC/MD lenses and adaptor; various "toy" lenses.

Well,
We ***might*** get to see one in action...
--> Mirrorless Rumors | Blog | Impossible may be possible? Nikon f/0.7 lens patent for the Nikon 1 system.

I wish I could remember. A university professor who specialised in optics told me some years ago but my memory is like a sieve.

But I have seen the f/0.7 quoted in magazine articles quite a few times since.

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Cub
Panasonic G3, 14-45mm, 20mm, 45-200mm, Olympus E-PL1, 9-18mm, 45mm

The simple answer: yes.

But there are some practical limits. Lenses become increasingly larger for smaller f-numbers, especially when they need to be used at different object distances. The reason is that the lens diameter is inversely proportional to the f-number. The second reason is that the lower the f-number, the more difficult it is to control the aberrations, and even more glass (extra elements, special glass) is needed for that.

For photo/film purposes, faster than f/0.95 is an extreme rarity. For fixed distance applications (like some technical imaging), f/0.7 does occur. Two imaging areas, however, excel in low f-numbers: microscopy and IC lithography. For both, equipment is available with f-numbers as low as 0.18 to 0.20. But these are highly specialized lenses, with almost fixed magnification and working distance (measured in microns) and typical dof of a few hundred nanometers. That is a thousand times thinner than paper.