Focus Issue

Discussion in 'Digital Photography' started by THUTTER, May 13, 2011.

  1. THUTTER macrumors newbie

    Joined:
    May 13, 2011
    #1
    I dont know if someone can help me or not. I have a canon 50d.. and I have a hard time getting it to focus on my two children. It seems to always focus one child and not the other. I am sure this is user error so I am not sure how to fix it.

    as you can see with the picture one subject is clearly in focus and the other is not. For these photos I was using a canon 50mm lens.

    looking for any advice. :confused:
     

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  2. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #2
    Focus is basically a plane parallel to the imaging sensor. So, in an image like the one you have posted, focus can only be on one child or the other as they are different distances away. Depending on your depth of field it is possible that both will be in focus even though the focus plane is only on one of them.

    In short to get them both in focus shoot with a smaller aperture. So if you are currently using f/2.0 try using f/4.0.
     
  3. andalusia macrumors 68030

    andalusia

    Joined:
    Apr 10, 2009
    Location:
    Manchester, UK
    #3
    Honestly, neither of them look in focus to me. However the younger kid does look closer to being in focus than the other one.
     
  4. Designer Dale macrumors 68040

    Designer Dale

    Joined:
    Mar 25, 2009
    Location:
    Folding space
    #4
    I think the trouble is with the wide aperture you are using. I looked at the photo info of this shot in PhotoShop, and you shot this at f/2.0. That's really thin for an outdoor photo on a good day. I have an App on my iPod called Simple DoF that will calculate the usable depth of field on a shot given a few variables. Your lens is 50mm at f/2.0 and I guessed that you are about five feet from your subjects. That yielded a depth of field of around three inches. At that, if you nailed the focus on the eyes of the child in the front, anything behind the ear is going to go out of focus. Try shooting this at 5.6 or f/8.

    Dale
     

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