Diff. between Close-up Filters(diopters) and Telephoto Extenders

Discussion in 'Digital Photography' started by bhaskar, Aug 4, 2003.

  1. bhaskar

    bhaskar Guest

    Hi,
    Since Close-up Filters magnify the subject by factor of 1x,2x,4x etc
    and Telephoto Extenders multiply the focal length by factors of
    2x,1.5x etc.
    Don't both of these acchive the same effect ?

    I realise that I may be confusing magnification as achieved by the
    close-up lens
    versus varying (increasing) focal length length as achieved by
    Telephoto extenders.
    But isn't increasing focal length equivalent to magnifying ? Or are
    they seperate in optical terms ?If so, then in optical terms what's
    the exact difference ? What optical parameters
    change when a close-up filter is mounted or when a telephoto extender
    is mounted ?

    In what situation would one use a close-up lens and in what situation
    would
    one use a telephoto extender ?

    Also is the close-up filter in any way related to macro phtography ?

    Prosumer cameras like Powershots have macro functionality built in,
    but what
    is to be used for macro photography using a D-SLR say 10D ?
    Can the Canon 28-135MM IS USM lens be somehow used for macro
    photography or do
    I need special macro lenses ?

    And lastly is a close-up filter kit just a poor man's macro lens ?
    and is a tele photo extender a poor man's Super Tele (focal length >
    300) Lens ?

    Thanks in advance for all those who help out,
    Just a confused newbie.
    bhaskar
     
    bhaskar, Aug 4, 2003
    #1
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  2. Telephoto extenders allow say a 100mm lens to function like a slower,
    less sharp 140 mm lens. Things will appear to be 1.4 times closer. So
    something 14 feet away will look like something 10 feet away

    A Close up filter will not make the subject look closer. What it means
    is that something that you might be able to photograph at 18 inches and
    resulting in a small object occupying less than 10% of the photo area, can
    be photographed at 10 inches and still be in focus.

    Tele extenders make it look like you were closer and close-up filters
    let you get closer. Not exactly the same thing.

    All else being equal the close-up filter/lens (they are really
    supplementary lenses) will give better overall sharpness when photographing
    something that is to small to photograph properly at the minimum distance
    your lens will focus.
     
    Joseph Meehan, Aug 4, 2003
    #2
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