D O F assignment trouble

Discussion in 'Photography Beginners' Forum' started by DeadEye, May 16, 2007.

  1. DeadEye

    DeadEye TPF Supporters Supporting Member

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    My assignment is to take two pictures . First tripod mount camera place a subject and get two shots one with subject and background in focus the other subject only in focus.

    I tried lots of different distances of camera to subject the only one that I could get the background to blur good was very close to subject. Then was unable to get a focus on the backgroung when going from f5.6 on up.

    Backing up a bit I was able to get only slight blur on background at f5.6

    Camera is Canon xti with kit lens 18-55mm.

    What am I doing wroung or is it wroung lens for this?

    TIA Dead Eye
     
  2. Don Simon

    Don Simon TPF Noob!

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    You are not doing anything wrong. You are simply demonstrating what your tutor hopefully explained about Depth of Field before they set the assignment.

    When attempting to obtain a shallower depth of field, try to get close to the subject, and to get the subject far from the background (in other words if the background is a wall just behind them, don't expect it to be out of focus). You are unfortunately limited by having a maximum aperture of f/5.6, but it should still be entirely possible to produce shots with the background out of focus. But knowing the theory will really help.

    There's a DOF calculator here (bottom of the page) which might help in your task.
     
  3. Big Mike

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

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    Set up your camera on the tripod, close to the subject (but not too close) and the background fairly far away. Take one shot at the max aperture (F3.5-5.6) and then take another shot at F22. Each time, you should set your focus on the subject.
     
  4. Sw1tchFX

    Sw1tchFX TPF Noob!

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    I'm guessing your instructor told you to shoot at 55mm, and if not, you should. Less distortion, shorter DOF.

    As long as you have at least some separation between your subject and background at f/5.6 you'll be ok. Stop your lens down to its smallest aperture and you'll pull pretty much everything into focus. You're limited by your equipment, and that's good that you experiment with distances, many people don't know that the shorter the distance, the shorter the DOF.
     
  5. DeadEye

    DeadEye TPF Supporters Supporting Member

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    In the assignment shots If I remember right I am to Use same focal length and distance from subject for both shots only changing the f stop and shutter speed. I shot outside on water front setup on tripod went max zoom 55mm focused then stopped to 5.6 took the shot. then up to smallest AV another shot. BOTH were clear background. Background had a chair about 5 feet back and a railing about 15 feet back and water out to woodline a mile or so.

    SO I got closer to subject now I got a good blur on background at 5.6 but could not clear up background with f stop as I was to close.

    Ill go play with it more

    Thanks Much Dead Eye
     
  6. motcon

    motcon TPF Noob!

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    can you just simply post the images that you are trying to explain? would help to view them...
     
  7. D-50

    D-50 TPF Noob!

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    Feel free to hand these in as your work if you like.......
    [​IMG]

    [​IMG]
     
  8. DSLR noob

    DSLR noob TPF Noob!

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    He would'nt learn anyhting that way.

    Set it to 55 and 5.6 in Av mode. focus on an object that is really close ot the lens.... a foot or so outside on some surface where you can see trees/bushes in the background. Then in AV turn the dial till the aperture # gets as high as it can go (39 @ 55mm I think) then take the photo again. You need a tripod, and I'd use the 10 second timer to prevent tripod shake.

    Tip: push the depth of field preview button and look through the viewfinder, then adjust the focus ring on the manual setting to get the background and random object in the stopped down focus.
     
  9. Sw1tchFX

    Sw1tchFX TPF Noob!

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    You're kidding me? It doesn't fit the criteria anyway, you just focused further away.
     
  10. DeadEye

    DeadEye TPF Supporters Supporting Member

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    Ok Im learning now I switched to the big lens and tryed again shot at 75mm f32 and 75mm f4 when I stoped to f4 the viewfinder was still out of focus in background but took the shot and it came out focused.:hail:

    I thought it would come out the way it looked in viewfinder. Both pictures looked same in viewfinder
    [​IMG]

    [​IMG]
     
  11. DeadEye

    DeadEye TPF Supporters Supporting Member

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    Thank you for the tip. Can you explain it more. There is a way to preview the background focus by hitting a button before the shutter?
     
  12. Weaving Wax

    Weaving Wax TPF Noob!

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    Yeah, there is DOF preview on most modern cameras I believe. The one on my camera shows the amount of light hitting the film (film user here!) (aperture) and that can serve 2 purposes. Chosing the best aperture for the situation and the right DOF. The smaller the F# (bigger aperture) the wider the DOF, the bigger the F# number (the smaller the aperture) the smaller the DOF. The preview will make the viewfinder/preview screen I assume, darker as the blades close up more and more (you won't see actual blades, though). It is a good way to get used to Aperture/DOF.

    If any of this information has been said above I'm sorry, I did not read the entire thread...
     

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