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Thread: DOF directly related to aperture size?

  1. #1

    Default DOF directly related to aperture size?

    Pardon my noob qn.

    Im just wondering, i seen pictures with nice bokeh and checked the exif, it shows F2.8

    if i use a F2.0 settings (different cameras, different range) wil be able to achieve close to that kind of effect?

    cos the DOF is VERY shallow of F2.8 for that particular pic. Or there are more things to be considered for that kind of effect...

    Thanks in advance

  2. #2
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    Default Re: DOF directly related to aperture size?

    There are plenty of things to consider.

    The first is that strictly speaking the Depth of Field refers to the field of focus, so although that indirectly affects your out of focus areas, it is not strictly speaking the out of focus area itself.

    In terms of the variables that influence the out of focus areas of an image... the following all have factors to play in combination with each other:

    [1] Focal length (longer = more out of focus)
    [2] Distance of focus (closer = more)
    [3] Separation between subject/point of focus and background (greater = more)
    [4] Sensor size - 4/3, APS-C, FF (larger = more)
    [5] Aperture used (wider = more)
    [6] Lens design, to include number and type of aperture blades but other other intangible design elements as well (some lenses with factors 1 to 5 the same, exhibit different looking out of focus areas)

    And possibly one or two others I've forgotten :P
    Last edited by Jed; 28th February 2010 at 10:47 AM.

  3. #3

    Default Re: DOF directly related to aperture size?

    i think the most common ones are covered by jed.

    if you use f/2.0 on a compact camera, you will not get same dof, because of the sensor size.

    you WILL get the same amount of dof if you use same lens, same focal length, same aperture... on crop frame sensor or full frame sensor.

    but of course crop frame sensor takes a crop out of the centre. i'm sure it's not that hard to visualise.

  4. #4

    Default Re: DOF directly related to aperture size?

    ahhh i see... given the limits of my cam, guess i shall play around with the distance:

    [2] Distance of focus (closer = more)
    [3] Separation between subject/point of focus and background (greater = more)


    thanks!

  5. #5
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    Default Re: DOF directly related to aperture size?

    The LX3 should be able to give decent bokeh if you work on points #2,3.

  6. #6

    Default Re: DOF directly related to aperture size?


  7. #7

    Default Re: DOF directly related to aperture size?

    it depends on your lens "sweet spot"

  8. #8

    Default Re: DOF directly related to aperture size?

    you can google for your lens informations, reviews, sample shots, etc.. where is the sweet spot

  9. #9
    Senior Member ZerocoolAstra's Avatar
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    Default Re: DOF directly related to aperture size?

    Quote Originally Posted by zichuan View Post
    it depends on your lens "sweet spot"
    huh? care to explain that?
    Exploring! :)

  10. #10

    Default Re: DOF directly related to aperture size?

    i think he meant which F the lens is at its sharpest... sweet spot...
    which is not what the TS is asking i guess.

  11. #11
    Senior Member ZerocoolAstra's Avatar
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    Default Re: DOF directly related to aperture size?

    yeah.. that's what I was thinking... sharpness (referring to 'sweet spot')and depth-of-field (relating to TS' question) aren't quite the same thing...
    that's why I was puzzled when "sweet spot" got mentioned in response to TS' question...
    Exploring! :)

  12. #12

    Default Re: DOF directly related to aperture size?

    Quote Originally Posted by mikeeeey View Post
    Pardon my noob qn.

    Im just wondering, i seen pictures with nice bokeh and checked the exif, it shows F2.8

    if i use a F2.0 settings (different cameras, different range) wil be able to achieve close to that kind of effect?

    cos the DOF is VERY shallow of F2.8 for that particular pic. Or there are more things to be considered for that kind of effect...

    Thanks in advance
    the technical answer to your thread title is nope..it is not directly related but rather INVERSELY related hehehe

  13. #13

    Default Re: DOF directly related to aperture size?

    Quote Originally Posted by zichuan View Post
    you can google for your lens informations, reviews, sample shots, etc.. where is the sweet spot
    This has zero to do with what the TS is asking. Please do not confuse the issue.
    Alpha

  14. #14
    Member Deloi's Avatar
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    Default Re: DOF directly related to aperture size?

    Quote Originally Posted by Jed View Post
    [1] Focal length (longer = more out of focus)
    if im using a 18-135mm as compared to a 18-55mm (assuming all other things being equal), will i get a better bokeh?

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    Senior Member 1912123's Avatar
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    Default Re: DOF directly related to aperture size?

    Quote Originally Posted by Deloi View Post
    if im using a 18-135mm as compared to a 18-55mm (assuming all other things being equal), will i get a better bokeh?
    Maybe photos can illustrate bokeh clearer. You can refer to the Bokeh Test done by dibyendumajumdar at his flickr website, he used 50mm, 85mm and 105mm with aperture settings from F1.4 to F5.6 on Nikon / D300. Can you tell the difference between different lenses and aperture settings?

    #1
    http://www.flickr.com/photos/2690472...7622808885458/
    #2
    http://www.flickr.com/photos/2690472...7622809195902/
    天国近了。
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  16. #16
    Senior Member ZerocoolAstra's Avatar
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    Default Re: DOF directly related to aperture size?

    Quote Originally Posted by Deloi View Post
    if im using a 18-135mm as compared to a 18-55mm (assuming all other things being equal), will i get a better bokeh?
    Since you said all things being equal, I assume you meant using 18-135 and 18-55 at the same focal length (eg. 55mm).
    If you're talking about 18-135 @ 135mm vs 18-55 @ 55mm, then to get the same field of view, you'll have to be standing much further away in scenario 1... thus, a lot of other factors come into play.

    regarding better bokeh, it's quite a subjective thing.
    The 18-55 will be at f/5.6 maximum at 55mm.
    I think the 18-135 @ 55mm will be larger than f/5.6, maybe f/4.8 or something.
    In that case the DOF should be thinner and you may get more subject isolation using the 18-135. I dunno about better bokeh though...
    Last edited by ZerocoolAstra; 2nd March 2010 at 11:10 AM.
    Exploring! :)

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