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Thread: Qns on Sigma 105mm Macro AF/MF

  1. #1

    Default Qns on Sigma 105mm Macro AF/MF

    Hi Guys,

    Could you guys help me with the AF/MF of this lens?

    There are 2 switches to switch between AF and MF. One at the focus ring and the other near the lens mount. What is the reason/function for the 2 switches? Can I switch one to AF and one to MF? Or I must set both to AF or MF only?

    Thanks in advance.

    Cheers.

  2. #2

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    Quote Originally Posted by AlvicTay
    Hi Guys,

    Could you guys help me with the AF/MF of this lens?

    There are 2 switches to switch between AF and MF. One at the focus ring and the other near the lens mount. What is the reason/function for the 2 switches? Can I switch one to AF and one to MF? Or I must set both to AF or MF only?

    Thanks in advance.

    Cheers.
    The switch is for you to switch between AF and MF. The rings are for you to Focus Automatically and Focus Manually. They serve different function.

  3. #3

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    So does it mean that when the switch is at MF, the focus ring should be also at MF? Likewise for AF?

  4. #4
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    IIRC, the AF/ MF switch on the camera is to stop it from providing power to auto-focus the lens. The AF/ MF switch on the lens body is to link the focus ring to the internal focusing mechanism. So you need to switch both to MF when you wish to manually focus.

  5. #5

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    Hi AlvicTay, how much and where u bought for the Sigma 105mm Macro lens? coz i intend to buy one.

    Thanks first .

  6. #6
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    Whatever position you leave the controls in , NEEVER EVER leave the AF/MF switch in AF and the ring in M becasue your EOS(?) will activate the motor for af-ing but isnce the ring is in M, it is engaged to the focusing mechanisim. Since the AF is active, the AF motor is ALSO engaged to the focusing mechanism, this is super bad news for the AF motor becasue it needs to now move a heavier load - which it is not designed for. You will know you are in this 'BAD' setting when you feel the focus ring moves while af-ing. STOP at once and disengae the focus ring to AF.

    Otherwise, not only your AF motor willbe damage, the focusing mechanism will wear out too.

  7. #7

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    So what is the point of have the AF/MF at the focus ring? Why not not it like normal prime/zoom lens with only thw switch at the mount?

  8. #8
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    Quote Originally Posted by AlvicTay
    So what is the point of have the AF/MF at the focus ring? Why not not it like normal prime/zoom lens with only thw switch at the mount?

    The AF/MF switch is the 'electrical' part of the system, it tells the body to activate the AF algorithem.

    The M and AF on the focus ring is the 'mechanical' part of the system, it engage/disengage the focusing mechanism to the AF motor.

    Some ppl who uses MF (mostly for macro) will disengage the focus ring from the focus mechanism while in MF mode. This is to prevent the focus from adjusting when focus has been set.

    The design is such, it is up to us to think of how to exploit it to our advantage.

    EF lens is simpler , with just a AF/MF switch, but it canbe accidentally adjusted out-of-focus if the focus ring is turned as it is engaged to the focus mechanism permernanatly.

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