Faking Infinity

Discussion in 'Beyond the Basics' started by Dmitri, Aug 30, 2008.

  1. Dmitri

    Dmitri No longer a newbie, moving up!

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    Hi, the canon kit lens doesn't have the much talked about Infinity setting. How would one fake it to do the near / far focus thing?

    Thanks.
     
  2. reg

    reg TPF Noob!

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    Focusing to infinity is just focusing really really far away for the focal length you're at (i.e. a 200mm focuses to 150ft before hitting infinity, a 28mm focuses to 30ft before hitting infinity but those numbers are just pulled out of thin air) unless you're talking about something else?
     
  3. Dmitri

    Dmitri No longer a newbie, moving up!

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    Supposedly it's a way to get near objects and far objects properly in focus.

    Edit: I should mention that it's technique usually associated with landscapes (or what I have read of it).
     
  4. reg

    reg TPF Noob!

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    That would be hyperfocusing, not infinity and that's just by going to a small aperture and focusing.
     
  5. Moglex

    Moglex TPF Noob!

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    The idea is that you focus your lens in such a way that objects at 'infinity' are at the minimum acceptable sharpness.

    This gives you the maximum range of distances at which objects are of acceptable sharpness.

    The distance upon which you focus is called the 'hyperfocal distance' and the range of acceptable sharpness goes from half that distance to infinity.


    See Here for a more detailed explanation.
     
  6. Dmitri

    Dmitri No longer a newbie, moving up!

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    Thanks a lot, Moglex. I'll check that out. :)
     
  7. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Google "DOF calculator", and you can find out what the approximate hyperfocal distances are for commonly used apertures and focal lengths. For instance 18mm @ f/8 are common settings when I'm shooting landscapes. I know the hyperfocus distance is about 7.5', and when I focus on something about 7' or 8' from me everything from 4' to infinity will be in the DOF.
     
  8. usayit

    usayit No longer a newbie, moving up!

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  9. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Yeah that's really cool. There are also probably DOF programs that can be uploaded to cell phones, etc...
     
  10. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    Well... that's not quite it. (no offense!)

    Hyperfocal focusing is focusing to infinity, and then pulling back a bit from there to get the objects closer to you in focus as well. It generally requires a range finder on the lens, but you can figure it out with some work and/or a rangefinder chart. (I've not done the chart thing, I just know it's possible)

    You can do hyperfocal focusing even with a very large aperature. It's also uber-sexy if you do, because the image will not suffer from as many light refraction issues.

    Info on hyperfocal focusing: http://www.great-landscape-photography.com/hyperfocal.html

    Focusing range chart: http://www.dofmaster.com/hyperfocal.html
     
  11. Alpha

    Alpha Troll Extraordinaire

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    Addendum to the above:

    The hyperfocal point is a sort of "false infinity." It's a focal point where everything beyond it is automatically in focus, per optical laws.
     
  12. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    Good point, and nice catch. Thanks, Alpha.
     

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