are you familiar with 'retrofocus' lens ?

Discussion in 'Photography Beginners' Forum' started by SimplyMo, Jul 17, 2008.

  1. SimplyMo

    SimplyMo TPF Noob!

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    i just read a bit about the retrofocus lens (design or attachment??) that is used with SLR camera lenses to enable the use with some wide angle lenses while allowing enough room behind the lens for the mirror to move.

    but. i am wondering. is this retrofocus thing a lens design or a lens attachment ???:confused: or both?

    and if it is an attachment, can it be used somewhat like a teleconverter, except to serve the opposite purpose on a 'normal focal length' lens? (an inverted teleconverter????)... making the normal focal length lens more of a wide angle(??)

    (thank you)
     
  2. SimplyMo

    SimplyMo TPF Noob!

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    i hope that made some sense!!
    please let me know if that was confusing....
     
  3. Mike_E

    Mike_E No longer a newbie, moving up!

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  4. Helen B

    Helen B TPF Noob!

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    It is a lens design. In simple terms a retrofocus lens (also known as an inverted telephoto) is a lens that has a focal length shorter than the distance from the back of the rear element to the image plane. It is usual for wide angle lenses for an SLR to be designed that way, so that the lens clears the swinging mirror.

    A telephoto (in the original sense of the word) lens is the opposite - it has a focal length that is greater than the distance from the front of the front element to the image plane.

    Typically the front part of a retrofocus lens has a negative (diverging) effect and the rear part has a positive (converging) effect. A telephoto is the other way round. If you look at the aperture of a retrofocus lens from the front it will appear smaller than from the back, and vice versa for a telephoto lens.

    You may see the front of the front element referred to as the 'front vertex' and the rear of the rear element referred to as the 'rear vertex'.

    Best,
    Helen
     
    Last edited: Jul 17, 2008

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