Focus issue, need help.

Discussion in 'Photography Beginners' Forum' started by MrsLittle, Jan 28, 2012.

  1. MrsLittle

    MrsLittle TPF Noob!

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    I was taking pictures today with my D7000 and 50mm 1.8g. I realized when I used a wide aperture, the focus was a bit off. I was focusing on the eye and the focus would be on the hair bow. I moved the focus point to the chin and then it was on the eye.
    Has anyone had this problem? Is it a camera problem or lens problem?


     
  2. Derrel

    Derrel Mr. Rain Cloud

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    It is a "common problem". At close ranges, shooting at f/1.8 means the depth of field is VERY shallow--so shallow that missed focus is common. It can be the result of the camera, the lens, the subject, or the photographer, or a combination of those factors. I am not kidding or joking--the AF system, the photographer, the lens, and the subject can ALL contribute to slightly-off focus results whenever shooting at close ranges at f/1.4 or f/1.8...there is almost no room for error at close distances at f/1.8 with a 50mm lens...on the part of anything or any person. Seriously.

    Stopping down a bit, like to say f/3.2 or f/3.5...the results are usually more "safe". At close distances, the DOF is still shallow at f/2.8 or f/3.2 or f/3.5, but there's just a little bit more leeway for errors, movement, etc,etc. The lens's performance might also get a slight bit better one full stop down from wide-open.
     
  3. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    To add on to what Derrel has said, have a look at this DoF calculator to get an idea of what your DoF is going to be at a specific aperture and subject-to-camera distance.
     
  4. MrsLittle

    MrsLittle TPF Noob!

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    Thanks Derrel. I was at 2.8 the whole time and didn't even think to change it once. It most likely is me, since I don't have the steadiest hands. I will try a smaller aperture next time and see how it works out.
     
  5. MrsLittle

    MrsLittle TPF Noob!

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    I have it printed out and take it with me everywhere. I haven't really memorized everything by heart quite yet. I think I might have been a little too wobbly when using that wide an aperture.
     
  6. MTVision

    MTVision Been spending a lot of time on here!

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    One thing that's helped me - even though it isn't really anything too technical - is to remember that the closer you are to your subject - the shallower the DOF. That's with pretty much any aperture. At f/11 and 4 ft. Away you are still going to have less then a foot of DOF.
     
  7. Rephargotohp

    Rephargotohp TPF Noob!

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    Other thing to consider is when you are bent over taking a shot of a little one, we sway back and forth, you won't even realize you do it but when you do, you move the point of focus, try to take a good photographers stance, or kneel down
     
  8. rokvi

    rokvi TPF Noob!

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    Burst mode if you can.
     
  9. KmH

    KmH In memoriam Supporting Member

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    Yep, about 8 inches total. And don't forget 45% of that DoF will be in front of the point of focus (3.7 inches), and 55% of it will be behind the point of focus (4 inches) .

    You also have to remember the plane of the DoF is always parallel to the image sensor. If the subject is at a slight angle to the image sensor, up and down or side to side, the DoF isn't.
     

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