2x teleconverters

Discussion in 'Beyond the Basics' started by KaraM, Jan 29, 2007.

  1. KaraM

    KaraM TPF Noob!

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    I have seen 2x teleconverters recently. Any comments or ideas about them? Are they worth the money? How do they affect shutter speed and/or aperature?

    Thanks,
    Kara
     
  2. darich

    darich TPF Noob!

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    I had a 2x Teleconverter. It was a Jessops own brand - decent enough but not the best. When i upgraded my lenses to "L" quality and my camera went from film to digital Rebel, 20D and now 5D i found that the teleconverter was by far the cheapest piece of glass in my kit.

    In general your shots are only as good as the cheapest item you use so i figured that having all the expensive gear and then using the tc was pointless. so i sold it.

    It depends on the gear you have and your budget as to whether it's useful. For me and my type of shooting i rarely used it and don't miss it. But others would.

    As for aperture and shutter speed - the aperture is set by your lens capabilities not the tc. However the shutter speed is affected because the tc reduces the light getting to the sensor so the shutter speed drops by a stop or two. Fast lenses are an advantage but you're then getting towards the situation i was in with expensive gear and something cheap in the equation.

    Autofocus is affected too. If your aperture is wider than around f4 autofocus is fine but less than that and the autofocus will not work. I stand to be corrected on the f4 part but it's around there somewhere, maybe f3.5

    They're worth the money in comparison to the cost of buying a longer lens. but if you have really expensive bodies and lenses then it wold be wise to buy a top of the range tc otherwise the quality of your lenses and body will be affected by the cheap tc in the middle
     
  3. Big Mike

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

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    I have one.

    As mentioned, the problem is that with slower lenses (F3.5-5.6) the use of a 2X teleconverter will most likely disable the auto focus capabilities. If you are using fast telephoto lenses (F2.8)...then AF will still work...but an F2.8 telephoto lens is probably a top of the line lens...and a cheaper TC will degrade the image quality.

    I haven't done any testing yet...but I want to see which will be better...my 70-300 lens with the TC...or just the 70-300 image cropped. If you are using digital and you don't plan on making huge prints...shooting without the TC and cropping...may be a better idea.
     
  4. Lars Leber

    Lars Leber TPF Noob!

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    I sometimes use a Sigma 2X on my Sigma 70-200 f/2.8. The autofocus still works well with that combination and I love that longer reach but the pictures lose some contrast and are slightly less sharp (these issues can be fixed in Photoshop though). The Sigma goes from 2.8 to 5.6 with the 2X.
     
  5. SaSi

    SaSi TPF Noob!

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    Check out this test gallery. http://www.pbase.com/drip/lens_tests
    I found this englightning.

    The bottom line is that a budget lens coupled with a 2x TC will suffer in every respect. AF will go away, sharpness will be measured in softness, CA will become apparent.

    On the other hand, a top-of-the-line lens will graciously accept a 1.4x TC with very low IQ drop and a 2x TC will make the lens into a rather good tele of twice the focal length.

    TCs were made for High end Telephotos, to double their role. Nobody says we cannot use them in cheap lenses, but we must know the limits.

    PS. I have stacked 4 2x TCs on a 1000mm mirror lens to make what is a 16000mm telephoto. So dark I can only shoot the sun, and this is why I built it.
     
  6. fmw

    fmw No longer a newbie, moving up!

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    My experience with 2X converters is negative, including expensive Nikon converters. The 2 stop light loss is pretty much an insurmountable problem with telephoto lenses and the image degradation is certainly visible. On the other hand, I've had very positive experience with the 1.4 or 1.5X converters. I've used both the Nikon and the Tamron. There is only one stop of light loss and the image quality is decent.
     

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