Aperture and DOF

Discussion in 'Beyond the Basics' started by ShutteredEye, Jun 7, 2005.

  1. ShutteredEye

    ShutteredEye TPF Noob!

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    Probably showing my noobile tendancies here, but can someone answer this for me?

    I understand that apeture affects DOF, that a wide open aperture results in a small DOF, and a small aperture gives a large DOF.

    My question is, in an SLR, while composing the picture and adjusting the aperture, should I see the effects of this changing DOF in the viewfinder?

    I would break out the SLR and try and figure it out myself, but I'm stuck in class. Biochem. Ugh.
     
  2. Artemis

    Artemis Just Punked Himself

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    No, unless (Like 300D and 300V Canon cameras) you may have a Depth Of Field Preview, but this simply shows how dark the picture is, and you work it out from there.

    But...to be answer your question...no...
     
  3. Unimaxium

    Unimaxium TPF Noob!

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    Like Artemis said, you generally should not see the DOF when looking through the viewfinder. The aperture is supposed to stay wide open until the shutter is released (in order to make the viewfinder brighter and to make focusing easier due to the smaller DOF). Some cameras, however, do have a DOF preview button on them which will temporarily close the aperture to whatever it's set at until you let go of the button.
     
  4. ferny

    ferny TPF Noob!

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    DOF Preview buttons give you a preview of the DOF. They don't show you how dark the picture will be because with correct exposure the picture will be no darker at different apertures. It may be hard to see, but they do show you what the DOF will be when you press the shutter.
     
  5. Meysha

    Meysha still being picky Vicky

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    Ahh that's something I've always wondered too. So when you focus on something does the DOF center on that.... or is the DOF always in the same spot of the photo.

    Argh! that doesn't make sense. What I mean is does the DOF move around the photo or is it always in the same spot.
    Hmmm writing this - I'm starting to think that the dof is just the width of the focus.... so you can focus anywhere (within your lens' capability) and the DOF is the width of that focus.

    Wow anyone else confused? :confused:
     
  6. ferny

    ferny TPF Noob!

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  7. ShutteredEye

    ShutteredEye TPF Noob!

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    uhhh....what link?
     
  8. Big Mike

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

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    You've got it right Meysha, DOF is just a width (distance from the camera) that is in focus. It doesn't matter where in the frame the objects are, if they are within the DOF, they will be in focus. As for how that all works, there is something called the circle of confusion, you will have to ask Hertz for an explanation on that one.
     
  9. Artemis

    Artemis Just Punked Himself

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    Think of it as levels in a picture...for example.


    IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Is a photo..
    IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
    Low aparature
    IIIIII
    High aparature...as you can see the lines represent what is in focus certain distance from camera....
     
  10. probe1957

    probe1957 TPF Noob!

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    It seems you might be a tad confused, yes.

    Depth of field is simply the distance from the nearest object in focus to the farthest object in focus.

    For example, and these are just numbers I am pulling out of the air...if you set your lens at f4 and focus at 25 feet, objects from 12 feet to 35 feet might be in focus. So your depth of field in this case would be 12 to 35 feet.

    Depth of field changes with aperture and focal length. For example, using the same prime lens as in the above example, focusing on a subject 25 feet away but changing your f stop to f16, objects from 4 feet to infinity might be in focus, so you depth of field is now 4 feet to infinity.
     
  11. ferny

    ferny TPF Noob!

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    The one I lost when I edited the post last time. :oops:

    I put it back.
     
  12. etaf

    etaf TPF Noob!

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