How to achieve extremly low DOF (Portaits)?

Discussion in 'The Professional Gallery' started by cumi, Dec 6, 2005.

  1. cumi

    cumi TPF Noob!

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    Hi!

    I saw a lot of nice portaits here with very low DOF and a very blury background, like here:

    http://www.thephotoforum.com/forum/showthread.php?t=36040

    or

    http://www.thephotoforum.com/forum/showthread.php?t=36152 (#2 pic especially)

    I am trying to achieve this with my PowerShot A520, but without any success yet. Any tipps? What am I doing wrong? I could achieve a low DOF only in macro-mode, but I don't think I have to take portaits in macro-mode.

    I can post some photos with settings if needed...

    I'am also going to try it with my old equipment (35mm film on Canon AV-1, 50mm 1.8 and 70-210 4.0). Is it a better idea?

    Thanks,
     
  2. LaFoto

    LaFoto Just Corinna in real life Staff Member Supporting Member

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    Shooting with a long focus should give you the desired blurred background.
    But if you want to stay digital, try to change the settings on your Powershot. You have a little ring there on top. And if all Powershots are more or less the same, then it should read (next to "Auto") P, TV, AV, M, C etc.

    Go to AV and set your aperture manually. My Powershot A95 allows for f2.8 at the lowest, provided I am have not zoomed. The longer the zoom, the less wide the aperture.

    If you then go to M, set the time required as you feel it might be right and half-press the shutter release button. The camera will then tell you if you are exposing just right, of if you are underexposing or overexposing by some steps. As long as the numbers that show are white, you are ok (and can deliberately overexpose or underexpose). If they turn red, the camera tells you: "Watch out, this is not right."

    But if you want to use your 35mm camera, taking your portrait shots from far away with the extended zoom lens should also give you a nicely blurred background. All you need is enough light then. And a willing model ;).
     
  3. danalec99

    danalec99 TPF Noob!

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    I was actually going to suggest a similar route. :)

    Just slap the 50mm on your SLR and shoot wide open (f1.8 ). You are going to love the ride! :)
     
  4. cumi

    cumi TPF Noob!

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    What do you mean here? Long focal length? I think the focal length doesn't changes the DOF only the perspective. If I want to have 1m long object on my photo, I have to take it at 35mm at 1m... or at 4m distance with 140mm. The DOF stays almost the same at same aperture.

    Exactly that's what I am doing. I'm shoting mostly in Av-mode. I am trying at F=2.6 and still no blurred backgroud, as you can see here (the background outside is quite "clear" :x :

    [​IMG]

    File: IMG_1243.jpg
    File size: 112KB
    Image Serial Number: 112-1243
    Camera Model: Canon PowerShot A520
    Firmware: Firmware Version 1.00
    Date/Time: 2005:11:26 15:47:30
    Shutter speed: 1/80 sec
    Aperture: 2,6
    Exposure mode: Av
    Flash: Off
    Metering mode: Center-weighted average
    Drive mode: Single frame shooting
    ISO: Auto
    Lens: 5,8 to 23,2mm
    Focal length: 5,8mm
    Subject distance: 4,87 m
    AF mode: Single AF
    Image size: 480 x 640
    Rotation: none
    Image quality: Superfine
    White balance: Auto
    Picture Effect: Normal
     
  5. Big Mike

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

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    Actually, the focal length does affect the DOF. The longer the lens, and the closer the subject...the shallower the DOF. So open up the aperture, zoom out and get close to your subject.

    The problem is your camera. The sensor is so small that it's very hard to achieve what you would consider a shallow DOF. You can do a few things to minimize the DOF...but your equipment is holding you back.

    I also suggest that you try the 35mm camera with the 50mm F1.8 (at F1.8 )...that should make a big difference.
     
  6. Tally Ho

    Tally Ho TPF Noob!

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    (Cut and paste) "I think the focal length doesn't change the DOF only the perspective." The longer the focal length of the lens the less DOF you will have at any aperture. Conversely, the shorter the lens the more DOF will you have at the same aperture. A wide angle lens will give you the maximum DOF of any lens at any aperture, but especially at F 11 or 16 or 22. You exposed this image with a wide angle lens. In order to use a longer lens, you will need to physically get further away from the subject in order to maintain the same size of your subject as in the original image. Photoshop has several ways to make a fuzzy background out of a sharp one.

    TH
     
  7. cumi

    cumi TPF Noob!

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    1. Example:

    Focal length = 35mm
    Subject distance = 1m (so I catch 1m on my photo)
    Aperture = 5

    DoF = 0.04 m

    2. Example:

    Focal length = 140mm (4xoptical zoom)
    Subject distance = 4m (I have to move back to catch 1m on my photo again)
    Aperture = 5

    DoF = 0.04 m

    So the DoF is same at both examples.

    I used this link for my calculations:

    http://www.dofmaster.com/dofjs.html
     
  8. Christie Photo

    Christie Photo No longer a newbie, moving up!

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    Remember... most of the DoF will be behind your point of focus. In the photo you posted of the girl by the window, it appears that the sign on the window is the point of focus. The focus on her is softer than the window frame. So, turn off the auto-focus.

    Recap: Longer lens, maximum aperature, and deep composition (keep subject far from background) will give you the results you want.

    -Pete
     

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