Canon D30, Sigma 300-800 and teleconverter

Discussion in 'Digital Discussion & Q&A' started by Kevin Barrett, Apr 26, 2007.

  1. Kevin Barrett

    Kevin Barrett TPF Noob!

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    My wife has a Canon 30D and a the Sigma 300-800mm Zoom lens. I would like to get a 2x teleconverter for it but I want it to retain the auto focus capability throughout the 300-800 Zoom range.

    Is there a teleconverter that will do this? Sigmas will not (and I don't think Canons does either).

    Thank you in advance.

    Kevin
     
  2. YellowBay

    YellowBay TPF Noob!

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    Hi Kevin,
    Niiiiiice Lens.
    I don't think anyone does a converter for that lens which supports AF. In addition, the converters push the f values up to F8 for the 1.4x and F11 for the 2x. That makes for a pretty slow lens. Having said that, I'd go for it anyway. What are you planning to shoot?

    This might help.
    http://www.sigma-photo.co.jp/english/support/faq/condaitr.htm
     
  3. Big Mike

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

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    Welcome to the forum.

    It's not the teleconvertor itself that is the weak link...it's the camera. The camera needs a minimum of F5.6 (that amount of light) for the AF sensors to work. A TC, effectively steals light...so when you use the teleconvertor, you no longer have enough light for the AF sensors to work.

    I think that the top end Canon bodies have more sensitive sensors which can focus with less light...but not the 30D.

    Another thing to consider is that a TC will also steal some image quality. With that great lens, you might be better off to just shoot and crop rather than use a TC.
     
  4. lostprophet

    lostprophet No longer a newbie, moving up!

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    if you had a Canon EOS 1D or 1DS series body if would focus with a 1.4x converter with the middle focusing point
     

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