Help: Lens size > Filter size

Discussion in 'Photography' started by Craig Bailey, Jun 28, 2006.

  1. Craig Bailey

    Craig Bailey Guest

    Just bought a Canon AE-1 Program, the SLR I really _wanted_ to own back
    when I was an 8th grader infatuated with photography in 1982. ;) (Back
    then I had to settle for a Canonet 28, but that's another story.)

    I'm looking to get a UV filter for the lens, and am a little puzzled
    about what size filter(s) to get. The lens is a Canon 50mm. But a couple
    filters that came with the set-up are 52mm -- and they fit fine.

    I've noticed that I can't seem to buy 50mm filters.

    Is 52mm the correct/preferred size for a 50mm lens?

    To complicate matters, the set-up also came with a Canon 28mm and a
    Vivitar 75-205mm zoom. (Though the Vivitar also has "55mm" printed on

    What's the best scheme for buying filters/adapter rings? Should I stick
    to one filter size, and buy adapters for the other two lenses? What
    filter size should I get?

    Also: What filter size does the Vivitar take? 55mm?

    Thanks in advance for any help.
    Craig Bailey, Jun 28, 2006
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  2. Craig Bailey

    Joe Friday Guest

    Lens focal length (55mm, 28mm, etc.) and filter size are 2 totally separate
    measurements. Focal length is just that, the focal length of the lens. The
    focal length of a lens is defined as the distance in mm from the optical
    center of the lens to the focal point, which is located on the sensor or
    film if the subject (at infinity) is "in focus".

    Filters, on the other hand are measured according to the diameter of the
    front element of the lens. Wider lenses equal wider filters.

    This is, of course, assuming you are using screw-in filters. Larger lenses
    (300, 400, 500, 600 mm and larger) use drop-in filters toward the back of
    the lens body There are also other systems (Cokin, for example) which use a
    mount on the front of the lens into which different square filters (and/or
    vignettes) are dropped.

    Hope this info helps!!
    Joe Friday, Jun 28, 2006
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  3. Craig Bailey

    no_name Guest

    You're confusing two different dimensions. The "50mm lens" refers to the
    focal length.

    52mm is the diameter of the front thread. I've seen 50mm lenses with
    49mm front threads, 52mm front thread, and 55mm front thread.

    You get the filter size that fits the front thread.

    If it says 55mm on the front bezel, it takes a 55mm filter.
    no_name, Jun 28, 2006
  4. Craig Bailey

    dadiOH Guest

    That's the cheapest filters large enough to fit your largest
    diameter lens and step up rings for the smaller diameter lenses to fit the
    larger filters.



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    dadiOH, Jun 28, 2006
  5. Craig Bailey

    J. Clarke Guest

    Nitpicking here but they're measured according to the filter mounting
    ring--while large diameter front elements will necessarily have large
    diameter mounting rings the converse is not necessarily true.
    J. Clarke, Jun 28, 2006
  6. Craig Bailey

    Jimbo Guest

    It should say the thread size on the inside of the lens where the
    threads are or on the outside
    If $ is an issue buy the filter for the largest lens then get to
    adapter rings - best to have dedicated filters though.
    Jimbo, Jun 28, 2006
  7. My old Canon FD 50mm f/1.8 and FD 28mm f/2.8 have the same filter
    diameter. A friend has my old FD lenses at this moment so I'm
    not so sure of the measurements. I believe the filters are indeed 52mm.

    If you are not sure of the filter diameters of your lenses
    just take them with you to the shop. You can find plenty of
    skylight and UV filters for your FD lenses second-hand.
    Try those first before buying new.
    robert_pascual, Jun 30, 2006
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