Question about focus.....

Discussion in 'Photography Beginners' Forum' started by Southerngal, Jul 9, 2007.

  1. Southerngal

    Southerngal TPF Noob!

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    This pic is by no means a great pic, except for the fact that is of my daughter. It seems out of focus to me. I was focusing on her. Is it just me?
    I havent edited the pic at all.

    [​IMG]

    Another question not related to the pic.....when you are taking group shots, such as in a wedding, how do you ensure that the entire group is in focus? What focus mode should be used (other than manual, I dont trust my eye w/the important pics yet)? My manual is awful, and it really does nothing more than send me from one page to another.

    And when Im using my kit lens (18-135 f/3.5-5.6), since Ive heard from many people on this forum that it isn't that great, should I just get use to always using a tripod? Could my lens affect focus?
     
  2. WDodd

    WDodd TPF Noob!

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    I don't ever use manual focus when I am trying to focus on something specific as I find it too hard to tell focus through the viewfinder on my XT.

    When focusing on groups of people I just set my aperture value higher. This gives you a deeper range of focus, and then I just pick a person in the middle of the front row and go for it.

    Going with F/8 on the picture of your daughter would probably solve the focus issue. It looks fine to me though.
     
  3. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Your daughter appears, to me, to be in sharp focus. The background is out of focus but that's OK and helps in this case. The wood/bench that is closer than her, is also out of focus and that is also OK.

    Do you have a clear understanding of DOF (depth of field) and how it works?

    DOF is the range of distance from the camera that will appear in focus. In your shot for example, the DOF looks to start with the closest parts of your daughter and starts to drop off at her farther leg/knee.

    Every shot has a DOF...it might be a thin area, like in this case...or it might start at a certain distance and continue on to infinity. The thing that most determines the DOF is the aperture of the lens. A bigger aperture (lower F number) will mean a more shallow DOF. A smaller aperture, (bigger F number) will mean a larger DOF.

    So going to your question about a group shot...to get everyone in focus, it would be wise to use a smaller aperture. Of course it also helps if you have everyone as close together (same distance from the camera) as possible.

    Now, you can't just use a small aperture without realizing that when you close down the aperture, you need a longer shutter speed and/or more flash power to get a proper exposure.

    As for where and how to focus...I use the auto focus and I only use the centre point. I focus on a person's eyes/face and then move the camera to recompose the shot, then fire away. If it's a group shot (and I want them all in focus), I will usually focus on the face of the person who is closest. Think of the DOF as it relates to the point where you are focused. The DOF will extend 2/3 past the focus point and 1/3 back to the camera. So if you have a big group shot and you can't use a really small aperture...you could get the most out of your DOF by focusing on someone who is 1/3 of the way into the group.

    I forgot to mention somw other things that affect the DOF. The focal length of the lens and the distance to the subject. A longer lens will have a smaller DOF and the closer you are to the subject, the more shallow the DOF will be.
     

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