Which autofocus motor to use?

Discussion in 'Photography Beginners' Forum' started by DScience, May 27, 2009.

  1. DScience

    DScience No longer a newbie, moving up!

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    Hello,

    I broke down (again) and sold my D60...the two zoom lenses...but, I kept my prime and got a new D90!

    Since both the AF-S lens and the camera have AF motors built in, which do I use? Should I set my lens to manual focus, and let the camera do the job? Or can I leave them on autofocus? Is there a difference?


    Here's a test shot, making things work.

    [​IMG]
     
  2. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    errrrrrr what?

    Is that even an option?

    No, it can't be. The AF-S lenses shouldn't even have a focusing screw on them. Your camera will use the internal focus on the lense if available, else it will use the internal-to-camera focus motor.
     
  3. DScience

    DScience No longer a newbie, moving up!

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    Ummm No, the AF-S lenses have a switch that allows you to manually focus the lens.
     
  4. DScience

    DScience No longer a newbie, moving up!

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    Ok, so I just tried to shoot with it switched to manual focus, and it would not AF. So here is the question, when using an AF-S lens, will it only use the AF motor on the lens? Is there a difference in the two? I would have thought the camera had a better AF motor.
     
  5. PhotoXopher

    PhotoXopher TPF Noob!

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    From everything I've read the lens motor is the way to go, it's generally faster and more quiet than the on camera motor.

    The only benefit to having the on camera motor is to use older lenses.
     
  6. Montana

    Montana TPF Noob!

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    Switching the lens switch to manual does just that, nothing should autofocus. And I agree that the lens motor, if equiped, should do the focusing.
     
  7. tsaraleksi

    tsaraleksi TPF Noob!

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    Manual means YOU are doing the focusing, with the focus ring. If there is any AF going on, it's the internal motor.
     
  8. DScience

    DScience No longer a newbie, moving up!

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    I'm not sure if you misunderstood my post. I know that when you put the lens in 'M' mode, it's manual focus for the lens, as this was the case with my D60. But what I don't get, is since there are TWO autofocus motors involved in the equation, do they both work? Or, does the camera default to the lenses AF motor once a AF-S lens is attached?

    The reason this is confusing to me, is because I thought the AF motor in the camera became better as you get higher quality cameras. I mean, every one talks about the 1D markIII being a super fast auto focus camera. This tells me there are different qualitites to an AF motor. I just don't understand how a lens AF motor would be 'higher quality' than the cameras contained motor.
     
  9. djrichie28

    djrichie28 TPF Noob!

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    An AF-S lens only has one option to focus. The built in motor.

    AF lenses have a screw drive if you look at the contact rim that lines up with certain cameras that have a built in focus motor. That really is it.

    The only reason that I can see why an AF-S lens has switches on the side, are for quicker access.

    I just looked at my 18-200 AF-S lens and there is not a 'screw' drive on the contact rim for the camera to even drive the focus from the camera. Therefore, the only way for this AF-S lens to focus is with the built in motor to the lens it self.

    If cameras get reviews on high AF speed, that is because the camera is fast at sensing focus. The camera always senses focus and not the lens. The camera communicates with the motor inside the AF-S lens and tells it what to do to achieve the focus.

    There isn't any way to control which motors drive the focus that I know of. By default, an AF-S lens will always use it's built in motor, while AF lenses will rely on the the screw drive and the camera motor (if the camera is equipped) to drive the focus. Smaller Nikon cameras don't have the built in drive, and that is why the can only focus using AS-F lenses.
     
  10. Steph

    Steph No longer a newbie, moving up!

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    If you mount an AF-S lens, it can NOT use the AF motor built-in the camera (there is not any mechanical connection between an AF-S lens and the camera body to allow for AF). AF will be performed by the motor in the lens. You cannot choose.

    As for Canon cameras (such as the 1D markIII), none of them have an AF motor built in the camera body. All the Canon lenses have an AF motor built in them.

    The speed of AF will not only depend on the AF motor but also on the AF sensor and all the electronics behind it.
     
    Last edited: May 28, 2009
  11. manaheim

    manaheim Jedi Bunnywabbit Staff Member Supporting Member

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    Right. Meaning manual focus. As in "using your hands".

    I mean steph really covered it so there's no reason for me to hop in here other than that I'm kind of even more baffled by this thread than I was last night. :)
     
  12. DScience

    DScience No longer a newbie, moving up!

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    You said the AF-S lenses don't have focusing screws built in, and in fact they do, so that you CAN 'use your hands' to focus.



    Steph, thank you that explains EXACTLY what I was curious about. Much appreciated!
     

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