50ft adapter lens

Discussion in 'General Airgun Chat' started by RAIDER, Nov 4, 2012.

  1. RAIDER

    RAIDER Member

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    Im sure on here once i read what the optical no was for the leupold 50ft adapter. im thinking it was like .08 of an optic what ever that means.
    RAIDER
     
  2. rich

    rich Active Member

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    0.0656 dioptre. :)
     
  3. PaulD

    PaulD I like Feinwerkbau's

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    Dunno what diopter it is but it works :rolleyes:
     
  4. rich

    rich Active Member

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    It looks flat to the human eye but it isn't. It's a very slight positive lens, that is, fatter in the middle than at the edge.

    It's got a focal length of 50 feet. Parallel rays of light entering the lens would be concentrated into a spot, 50 feet behind the lens.

    The dioptre number is the reciprocal of the focal length in metres. A lens with a focal length of 1 metre has a dioptre strength of 1. A lens with a focal length of 500 mm is known as 2 dioptres, being 1 divided by 0.5 (metres).

    The CFA focal length in metres is 50 ft divided by 3.281 to get it into metres, close to 15.24. The reciprocal of 15.24 (the 1/x button on the calculator) is 0.0656.

    How they manage to grind a lens to such precision defeats me, maybe that's why they are so expensive, they probably get a high proportion of rejects.
     
  5. RobF

    RobF Administrator Staff Member

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    Thought they were plastic these days...
     

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