Re: How are zoom lenses driven?

Discussion in 'Digital Photography' started by Eric Stevens, Sep 30, 2008.

  1. Eric Stevens

    Eric Stevens Guest

    On Mon, 29 Sep 2008 21:24:08 -0500, "J.C." <> wrote:

    >I'm having weird trouble finding usable diagrams of "super zoom" internals,
    >or any zoom for that matter. Cutaways show the glass and OIS, but how are
    >the sleeves aka barrels actually moved?
    >
    >I imagine it would either be rack & pinion, with cogs in a straight line on
    >a sleeve and motorized gears grabbing them from the sides. Or is it rubber
    >friction rollers on the barrel, like a tape deck drive?
    >
    >Specifically, what motor/gear system powers 12X+ Lumix/Leica lenses? My
    >camera is a FZ18. Any links to diagrams would help. Thanks.
    >

    There is usually a rotary cam somewhere, which works like a coarse
    thread to move something backwards or forwards.



    Eric Stevens
     
    Eric Stevens, Sep 30, 2008
    #1
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  2. Eric Stevens

    Paul Furman Guest

    Eric Stevens wrote:
    > On Mon, 29 Sep 2008 21:24:08 -0500, "J.C." <> wrote:
    >
    >> I'm having weird trouble finding usable diagrams of "super zoom" internals,
    >> or any zoom for that matter. Cutaways show the glass and OIS, but how are
    >> the sleeves aka barrels actually moved?
    >>
    >> I imagine it would either be rack & pinion, with cogs in a straight line on
    >> a sleeve and motorized gears grabbing them from the sides. Or is it rubber
    >> friction rollers on the barrel, like a tape deck drive?
    >>
    >> Specifically, what motor/gear system powers 12X+ Lumix/Leica lenses? My
    >> camera is a FZ18. Any links to diagrams would help. Thanks.
    >>

    > There is usually a rotary cam somewhere, which works like a coarse
    > thread to move something backwards or forwards.


    Argh, there's a better word but yeah you described what I found in the
    focusing mechanisms of old lenses I've dissasembled (focus is the same
    as zoom). I've got an old slide projector lens with the coarse thread
    groove and a metal dowel to follow that which is rather crude compared
    to a smooth gliding manual focus lens but that may be the solution for
    AF lenses which need to be able to move with less friction. For manual,
    friction gives more control, for auto it requires big heavy motors.

    Sorry no real help.

    Ah the word is 'focusing helix' I think.
    http://images.google.com/images?hl=en&q=focusing helix


    --
    Paul Furman
    www.edgehill.net
    www.baynatives.com

    all google groups messages filtered due to spam
     
    Paul Furman, Sep 30, 2008
    #2
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  3. Eric Stevens

    Paul Furman Guest

    Paul Furman, Sep 30, 2008
    #3
  4. Eric Stevens

    Eric Stevens Guest

    On Tue, 30 Sep 2008 20:28:53 -0500, "J.C." <> wrote:

    >Eric Stevens <> wrote in
    >news::
    >
    >> On Mon, 29 Sep 2008 21:24:08 -0500, "J.C." <> wrote:
    >>
    >>>I'm having weird trouble finding usable diagrams of "super zoom"
    >>>internals, or any zoom for that matter. Cutaways show the glass and
    >>>OIS, but how are the sleeves aka barrels actually moved?
    >>>
    >>>I imagine it would either be rack & pinion, with cogs in a straight
    >>>line on a sleeve and motorized gears grabbing them from the sides. Or
    >>>is it rubber friction rollers on the barrel, like a tape deck drive?
    >>>
    >>>Specifically, what motor/gear system powers 12X+ Lumix/Leica lenses?
    >>>My camera is a FZ18. Any links to diagrams would help. Thanks.
    >>>

    >> There is usually a rotary cam somewhere, which works like a coarse
    >> thread to move something backwards or forwards.

    >
    >Can you be more specific or direct me to an image? I'm now picturing a non-
    >round (rubber?) roller grabbing the inside of the barrel at its high
    >points.
    >
    >What I'm mainly trying to find out is whether these are hard-gear driven,
    >and subject to stripping (of said gears) if the lens is moved manually.
    >

    I don't think there is any single simple answer to your question. It
    all depends on the lens.



    Eric Stevens
     
    Eric Stevens, Oct 1, 2008
    #4
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