Plastic vs metal lens mount

Discussion in 'Digital SLR' started by Sheldon, Jul 4, 2005.

  1. Sheldon

    Sheldon Guest

    I've noticed that some manufacturers are using a plastic lens mount on DSLR
    lenses. I realize this isn't a "normal" plastic, but how long can something
    like this be expected to hold up and last?

    Obviously, if you never swap lenses it will last forever.

    Sheldon
     
    Sheldon, Jul 4, 2005
    #1
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  2. Sheldon

    Stacey Guest

    It won't..
     
    Stacey, Jul 4, 2005
    #2
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  3. Sheldon

    RichA Guest

    Plastic is GARBAGE in certain situations and since it is almost always
    used to cut costs, you KNOW it won't hold up like metal. There are
    composites that have some stability and rigidity, but they cost more
    than aluminum or s/s so you'll never see them in an average camera.
    I remember years ago when a cheap SLR (Canon T70?) used a crappy
    aluminum lens mount instead of chrome-plated brass and everyone
    complained about it's wear problems. In addition, plastic has other
    ugly characteristics that make it second-rate as well, such as
    too much thermal expansion and contraction. Also, unless it's
    machined, it generally does not have the precision of metal since all
    plastics change shape slightly when cast, blow molded, etc.
    Check out Ford's recent $750m problem with plastic V8 intake
    manifolds. Plastic is trash, it's cheap and easy to make and form,
    so it makes up the bulk of inexpensive consumer cameras.
    The next horror made of plastic will be molded aspheric lens
    components in lower-grade DSLR lenses. Why? Because it costs pennies
    to mold an acrylic lens versus up to hundreds of dollars to grind an
    asphere in glass. Since the camera makers don't really work to make
    lenses that accurate, and love to cut costs, it must make them angry
    that they can't find plastics of suitable refractive index to replace
    all-glass lenses.
    -Rich
     
    RichA, Jul 4, 2005
    #3
  4. RichA wrote:
    []
    My glasses have plastic lenses (I think) which appear to be hard-wearing,
    and very light considering the high refractive index. OK, they are not
    aspheric, but why should I be worried about such materials inside an
    optical system?

    David
     
    David J Taylor, Jul 4, 2005
    #4
  5. Manufacturers of styrene-allyl alcohol co-polymer say "hi."
     
    Steve Cutchen, Jul 4, 2005
    #5
  6. Sheldon

    Andrew Haley Guest

    Nikon have been doing this since 1991, with the 28-70mm zoom.
    According to the Nikon Compendium, way back in 1968 the 10mm f/5.6 OP
    had a plastic element.

    I don't think it's such a wicked thing to do.

    Andrew.
     
    Andrew Haley, Jul 4, 2005
    #6
  7. Andrew, could you please be more careful in your quoting? It was RichA
    who made the "horror" comment, not me.

    I'm glad to hear that Nikon may indeed be ahead of the rest in using the
    most appropriate optical components for the job.

    Thanks,
    David
     
    David J Taylor, Jul 4, 2005
    #7
  8. Sheldon

    RichA Guest

    Glasses are probably the least demanding of all optical elements.
    They can be out of spec by a large margin and still work well.

    They are already experiencing the problem of lenses not living up to
    the capability of the sensors out there. Adding plastic lens elements
    to the mix won't help matters. All lenses will eventually have to
    incorporate ED elements (and the heavy flint components needed to
    match with them). Plastics don't help, especially if the lens has
    any kind of magnification factor (telephoto) which is where you need
    better optical correction.
     
    RichA, Jul 4, 2005
    #8
  9. Sheldon

    RichA Guest

    As a basic subsitute for crown glass, acrylic plastic
    is somewhat acceptable if the elements don't have much
    curvature on them. They've been used in things like
    home theatre projector guns where a 5" wide aspheric would
    be prohibitively expensive.
     
    RichA, Jul 4, 2005
    #9
  10. Sheldon

    Sheldon Guest

    "David J Taylor"
    There are special optical grade plastics used in lenses that work just fine.
    They just aren't used in the mount to hold the lens on. I'll bet your
    glasses have metal hinges and screws.
     
    Sheldon, Jul 4, 2005
    #10
  11. Indeed, yes. I wasn't querying the lens mount, but RichA's comment on the
    optics themselves.

    Cheers,
    David
     
    David J Taylor, Jul 4, 2005
    #11
  12. Sheldon

    Bubbabob Guest

    My 70-300 G has the plastic mount. It's holding up a lot better than I
    anticipated.
     
    Bubbabob, Jul 5, 2005
    #12
  13. Sheldon

    Slack Guest


    You are funny, if nothing else. Not only did I work for a (highly
    regarded) "plastics" manufacturing company, I currently work for a
    (highly regarded) Aerospace company. We are substituting metal with
    plastic more and more. I can assure you, if plastic was crap Boeing and
    Airbus would not be giving us approval to us it.


    To the OP: If the correct plastic is used, it could easily out last the
    camera itself.
     
    Slack, Jul 5, 2005
    #13
  14. To the OP: If the correct plastic is used, it could easily out last the
    Sure - if it's a Canon which lasts only 12-28 months ...
     
    Benedikt Schenker, Jul 5, 2005
    #14
  15. Sheldon

    Sheldon Guest

    I guess my point is that the quality of your lens mount is not something you
    should even have to think about.
     
    Sheldon, Jul 5, 2005
    #15
  16. Sheldon

    Bubbabob Guest

    True, and after having it hold up perfectly for a year, I don't think about
    it.
     
    Bubbabob, Jul 6, 2005
    #16
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