Is it physically possible to have a lens with an f/1?

Discussion in 'Photography Beginners' Forum' started by Senor Hound, May 12, 2008.

  1. Senor Hound

    Senor Hound TPF Noob!

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    I've never seen an f/1 lens. I was thinking about it, and it seems like it would be possible if you widened the lens body where the aperture is (though that might cause other problems)?

    Would this be possible? If not, why? And if so, why aren't there any around?
     
  2. rufus5150

    rufus5150 TPF Noob!

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    I know of one: Canon 50mm f/1.0L, and as far as I know, it was the only f/1.0 made for the EF mount (quick wikipedia check just confirmed this) and has been supplanted by the f/1.2.

    I can't answer your other questions.
     
  3. Dao

    Dao No longer a newbie, moving up!

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  4. Alex_B

    Alex_B No longer a newbie, moving up!

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  5. Battou

    Battou No longer a newbie, moving up!

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  6. Alex_B

    Alex_B No longer a newbie, moving up!

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    It is possible, and and you can go even below f/1.0, but of course the wider the aperture, the harder it gets to minimise CA and optimise sharpness. Also, there is only little demand for such lenses on the market as the depth of field of such a lens is extremely shallow and it is hard to use it effectively.
     
  7. Senor Hound

    Senor Hound TPF Noob!

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    It looks like there is a little bulge (must be Bulgarian... lol) where the aperture is. That's what I thought. I was kind of testing my physics (optics) knowledge when I asked this, so I think this confirms my belief on the subject...

    Now one with an f/0 would be infinitely large (can't divide by zero), and therefore would be impossible (an f/.1 is possible technically, but not possible physically, nor would it render any sort of noticeable difference).

    Thanks guys. I feel smart (gets off soap box).
     
  8. I have two, the Leica f/1 Noctilux, and the Canon f/0.95.

    They are primarily the result of a 1960s feature pissing match over who could build the fastest lens... sort of like megapixels were last year, or high ISO is right now.

    They're fun to use, but you better nail focus - the DOF is so shallow is to border on the unusable if you don't get it right.
     
  9. ...interesting Kubrick article, thanks for the link. I'd HATE to be the AC working as Focus Puller on a shoot using an f/0.7 lens...
     
  10. TamiyaGuy

    TamiyaGuy No longer a newbie, moving up!

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  11. Battou

    Battou No longer a newbie, moving up!

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    What mount is that .95 on?
     
  12. Helen B

    Helen B TPF Noob!

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    f/0.1 is not possible for a photographic lens. The theoretical limit is f/0.5* . Lenses faster than f/0.9 are very rare, and the famous f/0.7 that was used on Barry Lyndon is the fastest I have heard of in photographic or cinematographic practice. (note that they used rack-over focusing for that lens, not reflex focusing). I have a couple of Kern f/0.9 lenses for cine use, as well an Angenieux f/0.95 and a Noctilux. The Angenieux is quite common for 16 mm, and not expensive these days. Zeiss f/1.1 Master Primes are widely used for cinematography. The T-numbers of all thee lenses are less impressive, but they are still impressive for T-numbers.

    *I can explain it if anyone is interested - or you can work it out a few ways, the easiest being from the accurate definition of relative aperture. See this thread for the real definition of the 'relative aperture of a photographic lens'.


    Best,
    Helen
     

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