Lens hood

Discussion in 'Digital Photography' started by Denis, Sep 12, 2007.

  1. Denis

    Denis Guest

    What is the purpose of a lens hood and why the odd shape
     
    Denis, Sep 12, 2007
    #1
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  2. On Sep 12, 7:45 am, Denis <> wrote:
    > What is the purpose of a lens hood and why the odd shape


    Not all lens hoods have the weird shape. More on that later.

    When direct sunlight impinges on the front of the lens, it leads to
    artifacts called ghosts and flare, which reduce contrast of the
    image. Even multicoated lens surfaces always reflect SOME light. And
    interior parts of the lens and camera, in spite of being blackened,
    still reflect a few per cent. Since the sun is far brighter than any
    light source in the scene, sunlight bouncing around inside the camera
    eventually gets to the image chip. The more complex the lens (the
    more elements/surfaces) the worse flare (and ghosts) become. So the
    lens hood is a way to keep sunlight off the lens front when you are
    shooting with the sun to the side or in front of you.

    In order to keep sunlight off the lens with short focus (wide field of
    view) and zoom lenses, the shade would have to be VERY large, larger
    than many consider convenient.

    The fancy petal shaped sunshades allow you to have a reasonable
    sunshade that is useful for wider FOV images, though they do not work
    as well as a real, full size sunshade.
     
    Don Stauffer in Minnesota, Sep 12, 2007
    #2
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