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Thread: how to choose which f-value?

  1. #1
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    Default how to choose which f-value?

    hi,
    i am actually a little confused. Ive heard that for macro shots, i should use small f-values, like f-2. However, i do see ppl saying that we should use larger f-values instead, like f10 or 12. So what is right? Let say i want to achieve a shallow DOF with the background blur and subject in focus.

    Similarly, for landscape shots, i should use a larger f-value like f12. Right?

    Btw, i am using a al-cheapo A40.

    Thank you for helping me out!

  2. #2
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    Default Re: how to choose which f-value?

    Originally posted by Wryer
    hi,
    i am actually a little confused. Ive heard that for macro shots, i should use small f-values, like f-2. However, i do see ppl saying that we should use larger f-values instead, like f10 or 12. So what is right? Let say i want to achieve a shallow DOF with the background blur and subject in focus.

    Similarly, for landscape shots, i should use a larger f-value like f12. Right?

    Btw, i am using a al-cheapo A40.

    Thank you for helping me out!
    With a higher F value, the aperture is smaller. With higher F value, the area that is in focus will be greater.

    However, the DOF is narrower when doing close-up/macro.

    For landscape, most wanted the foreground and background to be in focus/clear, thus, most use f8-f22.

    For macro shot, higher DOF is desirable to get more details.

    A f16 for lanscape might have everything in focus. In macro, depending on how close you are to the object. A f16 might not get everything in focus.

    Click on my photosig pics, the "Shoot" is taken with f16 but some part is still soft.

    Hope this helps.

  3. #3

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    small f-stop means aperture is larger(f1.4 1.8 2 etc) gives u good background blur. (good being a subjective term) This is because only a shallow 'plane' is in focus ie little bit in front and little bit at back of pocus pt will also be in focus. everything else is out of focus.

    larger f-stop means aperture is smaller(f 11,16,22 etc) and more of what u see becomes shaper. effect easily seen if u have a dof preview function...most SLRs do have this, A40 i'm not sure. The focus plane is deeper ie more in front and behind the point of focus will be sharp.

    back to the issue.

    for macro, since the focusing distances aren't that great, whether or not to use a larger f-stop will depend on what u want. eg if taking a water lily or some other relatively large flower, maybe its a better idea to use an f-stop of 11 or 16 etc so the whole flower will be in focus. for smaller flowers. because of their smaller size, shouldn't need too small an f-stop as they will be in the region of focus.

    since you're using digital, experiment with the various f-stops and see which effect u like...

    happy shooting

  4. #4
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    Default

    ohh..thanks for advices given!

    Nope, A40 does not have a DOF preview

  5. #5
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    Originally posted by Wryer
    ohh..thanks for advices given!

    Nope, A40 does not have a DOF preview
    You dun need it. You can take the pic and view the DOF. Thought the LCD is small. I think can zoom in when viewing as my A20 can.

  6. #6
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    Default

    but i find that viewing the DOF is a little difficult. Especially during trips where i am under the strong sunlight. Furthermore, the LCDs' pixels make it hard to check the DOF. Really thank u guys for helping me out!

  7. #7

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    r i g h t.. i forgot. digital can just take the pic first then preview on lcd....


  8. #8

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    er......tot suppose to use bigger aperture [smaller F value] + zoom in for getting bokeh effect???

    just like taking landscape we use smaller aperture [larger F value]
    for more dof.

    but due to the fact [A40] that when u zoom in the aperture become smaller.....so very hard to get a decent bokeh effect.

    this is what i think all the while......
    DSLR newbie: 400D + Tamron 18-200mm + 50mm F1.8 (i simply love it!)
    Canon G2

  9. #9
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    Default

    Originally posted by Wryer
    but i find that viewing the DOF is a little difficult. Especially during trips where i am under the strong sunlight. Furthermore, the LCDs' pixels make it hard to check the DOF. Really thank u guys for helping me out!
    not sure ur cam support switching view mode to viewfinder, if so, strong sunlight is not a problem. heh, zoom in more to see the DOF...

  10. #10
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    Default

    Originally posted by digi~ET
    er......tot suppose to use bigger aperture [smaller F value] + zoom in for getting bokeh effect???

    just like taking landscape we use smaller aperture [larger F value]
    for more dof.

    but due to the fact [A40] that when u zoom in the aperture become smaller.....so very hard to get a decent bokeh effect.

    this is what i think all the while......
    the bokeh effect is easier to achieve using longer lens (usually 85mm onwards, they call it portrait lens) together wif a bigger aperature (small F value)

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