Extension Tube...?

Discussion in 'Beyond the Basics' started by S40T5Lover, Nov 13, 2008.

  1. S40T5Lover

    S40T5Lover TPF Noob!

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    Hey,
    I have a Nikon D50 and I have a Nikkor 70-300mm lens and I was wondering if there was some kind of extension tube for it that I could get that will make it zoom further...? I saw a guy at an airshow with a 300mm and he had some sort of attachment and it made it 500mm..... ?

    Thanks guys!
     
  2. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Teleconverters are what you are after. They multiply the focal length of a lens by a factor (1.4, 1.7 or 2 (ie double the focal length) to give you more reach. However they do reduce the light entering a camera - 1.4 loses you one stop of light - a 2 loses you two stops of light.
    Further they also reduce the end result from the lens - on a good lens a 1.4 will cause hardly any noticable loss of quality - and with only one stop of light lost 1.4 teleconverters are the most poplar and cost efficient.
    2 times teleconverters are a different beast- they lose you two stops and quality reduction is noticable even on top end pro lenses - that said with a top end pro lens you can normally get good consistant results with the combo.
    Mostly teleconverters work best with prime lenses where the optices are already very sharp - for zooms they are best left only to the very top end zooms - sadly the more budget line zooms just don't have the quality to work well with teleconverters - results are often as or poorer than just increasing the image size in editing.
    Also bare in mind that teleconverters to not work with all lenses so check the compatability before you purchase - some 3rdparty companies like sigma and tamron make good teleconverters that will work with a wider selection of lenses
     
  3. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    That's right, you are looking for a teleconverter. Extension tubes also go between the camera and the lens, but they are made for macro photography, so pretty much the opposite of what you want to do.

    As mentioned, teleconverters reduce the amount of light coming in. This can mean trouble for an already 'slow' lens like your 70-300mm. Most cameras need a lens with a max aperture of at least F5.6 in order to get enough light for the autofocus to work. So if you were to put a 2X TC behind that lens, you would only be getting about F11 light when zoomed all the way out...which probably isn't enough for your camera to auto focus.

    You could still manually focus the lens, but it might be harder to see clearly.

    This is why (as mentioned) TCs are most often used with prime or fast zoom lenses.
     
  4. S40T5Lover

    S40T5Lover TPF Noob!

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    Ahh, alright, thank you guys!
     

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