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Autofocus which subject does it focus on?

  1. May 29, 2012 #1
    autofocus....which subject does it focus on?

    Hello Forum,

    I was just reading and learning about autofocus. There are two types: active and passive, etc...
    But I am still missing on which subject on the scene does the camera decide to focus on?
    Focusing means changing the distance between the lens and the sensor until the image is the sharpest...but in a scene there are multiple subjects....which one does the camera pick?

    Have you guys heard about the Lytro camera? What do you think about it? You take a picture and focus only after that, on the part of the picture that we prefer...

  2. jcsd
  3. May 30, 2012 #2


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    Staff Emeritus
    Science Advisor

    Re: autofocus....which subject does it focus on?

    That depends on the type of system. An active system would focus on whatever the beam is bouncing off of. A passive system analyzes the picture and focuses, but on exactly what I do not know. It probably depends on the type of camera and the system and programming it uses.

    As for the lytro camera, it seems kinda cool, but there are significant disadvantages to it. I think it has its uses though.
  4. May 30, 2012 #3


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    Staff: Mentor

    Re: autofocus....which subject does it focus on?

    There is a wide variety these days. My camera can be "told" what my face looks like, then recognize and focus on it in a crowd.
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