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P3D focal length

  • From: Dylan The Hippy Wabbit <spacey@xxxxxxxxxxxxx>
  • Subject: P3D focal length
  • Date: Thu, 11 Feb 1999 10:50:44 +0000 (GMT)

Hi All,

Rod Sage wrote:-

>Could someone one the list tell me if there is a formula for converting
>close up lenses to focal length. For example, what is the focal legth of
>a +1,+2 etc. close-up lens. I guess these are diopters. Should I be
>asking how to convert diopters into focal length. I want to order some
>lenses from Edmund Scientific. Sorry if this should have gone to T3D.

The power in dioptres is equal to one divided by the focal length in
metres.  So +1 is 1000mm, +2 is 500mm and so on.  And a 50mm standard lens
is +20 diopters.

Dave Spacey

_____________________________________________________________________________

Of Bill Gates, "In fact, he's Ernst Stavro Blofeld as played by Woody 
Allen." - Charles Shaar Murray


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