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  1. #1
    Senior Member
    arshuter's Avatar

    Teleconverter question

    I use a D850 and Sigma 100 x 400 lens for most of my wildlife photography. I would like to extend my range a little. I have been studying and reading everything I can find on teleconverters. That said, most say that with this combination it's a guessing game as to weather your autofocus will work. Anyone have any real world experience with this? I realize I could go to a 150 x 600 but trying to keep weight to a minimum. Thanks, Alan


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  2. #2
    Staff
    Super Mod
    hark's Avatar

    Re: Teleconverter question

    What is the variable aperture on your 100-400mm lens? Does it go to f/5.6 or f/6.3 when it is zoomed out long? And what types of teleconverters does Sigma make that are compatible with that lens? You will need to use a Sigma TC, not a Nikon TC.

    The D850 has f/8 support which means you should be able to use a lens that is wide open up to f/8. So you'd have to determine what your lens' aperture is when zoomed out to 400mm then factor in how much light loss there is from the TC.

    My D500 has a 300mm f/4 lens (constant aperture, not a variable one) with a 1.7x TC. That means I lose 1.7 stops of light making my aperture f/6.7 wide open. Depending upon the contrast of my subject, sometimes it will hunt. But if your aperture will be f/8 wide open with a TC, I'm sure there will be some hunting going on.

    Please give us the details of your current lens' aperture and what length TC you are considering. That's where you need to start first.
    Cindy - D750, D500, D7200
    Flickr
    and My 2020 Thread

    Where the Spirit does not work with the hand, there is no art
    -- Leonardo da Vinci



  3. #3
    Staff
    Super Mod
    hark's Avatar

    Re: Teleconverter question

    And for the record, the Nikon 1.4x teleconverter only loses 1 stop of light. Not sure if a Sigma TC would offer the same amount of light loss or if it would be more. EDIT: Just found the info in the link below that the Sigma 1.4x TC has 1-stop of light loss.

    So I did a little digging and found this Sigma link for TC's:

    https://www.sigmaphoto.com/lenses/le...-compatibility

    If you have the Sigma 100-400mm F5-6.3 DG OS HSM Contemporary lens, it looks like the Sigma TC-1401 will allow the AF to work on cameras with the f/8 support, BUT there is an *6 next to it. Looking at the footnote, it states

    *6 When it is attached to cameras that are compatible with AF at F8, focus accuracy is not ensured on the telephoto side at the focal length scale more than 200mm.

    The Sigma TC-2001 (probably a 2x TC) lists that lens as being manual focus.
    Last edited by hark; 10-27-2020 at 01:46 PM.
    Cindy - D750, D500, D7200
    Flickr
    and My 2020 Thread

    Where the Spirit does not work with the hand, there is no art
    -- Leonardo da Vinci



  4. #4
    Senior Member
    arshuter's Avatar

    Re: Teleconverter question

    It is the 6.3. Yes I also found that info on Sigmas sight but saw somewhere that it will "auto focus with some lenses" not sure what that is supposed to mean.

  5. #5
    Senior Member
    mikew's Avatar

    Re: Teleconverter question

    I used the D500 with the Sigma 100-400 and Sigma 1.4 that set up was still very fast focusing
    Mike



    https://www.flickr.com/photos/[email protected]/


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