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Thread: Optimal F-Stop for Canon Lens

  1. #1

    Default Optimal F-Stop for Canon Lens

    Anyone knows where to get information on the optimal F-Stops for Canon Lens?

    I just got a 350D, and took me a few weeks to realise that I have to take pics around F8 on the kit lens to have a decent sharp photo. But then realise again that it may not be the same for all the focal range.

    Also I am hunting around for a new lens. Does it mean that I will also have to take at f8 to get the sharpest pic?

    Sorrie... newbie on the move

  2. #2
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    Default Re: Optimal F-Stop for Canon Lens

    Generally, it is right to say f8 - f11 will be optimal setting for most lenses. Of course they will be some exceptional cases.

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    Default Re: Optimal F-Stop for Canon Lens

    There is no hard and fast rule for this. Basically it is different with each lens. You will need to do a test with each lens you own. Use a newspaper to shoot as I find text is the best comparison for sharpness.

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    Default Re: Optimal F-Stop for Canon Lens

    Try the following link about f-numbers.
    http://en.wikipedia.org/wiki/F-number

    It does say that for most lens the optimal f-number is in the mid-range.

  5. #5

    Default Re: Optimal F-Stop for Canon Lens

    It varies from lens to lens but F8 is normally the sweet spot for most lenses. Anything more than F16 is generally bad though. One way to find out the sweet spot of your lens is to look at reviews like over at http://www.photozone.de/. However, i would take his test results with a grain of salt since he seems to have had quite a bit of variations in some of the lenses he has tested before. Anyway, don't worry too much about always using "sharpest" aperture value but rather more about how it affects the DOF/exposure (and thus the effect you're going for).

  6. #6

    Default Re: Optimal F-Stop for Canon Lens

    Thanks!

    Another question I have is when do we want to use a high f-stop (i.e. f16-32), since the DOF will be quite large, requires lots of light, and it is not necessary the sharpest f-stop of the lens.

  7. #7

    Default Re: Optimal F-Stop for Canon Lens

    Quote Originally Posted by jklo
    Thanks!

    Another question I have is when do we want to use a high f-stop (i.e. f16-32), since the DOF will be quite large, requires lots of light, and it is not necessary the sharpest f-stop of the lens.
    You basically answered your own question - when you require a large DOF! This is most obvious when you do macro shots: f-stop values typically start from f/16 onwards.

    And I quote Denosha:
    Anyway, don't worry too much about always using "sharpest" aperture value but rather more about how it affects the DOF/exposure (and thus the effect you're going for).

  8. #8
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    Default Re: Optimal F-Stop for Canon Lens

    I think there is too much preoccupation with the optimal f-stop or sharpest aperture. Rather I feel we should concentrate on how using various apertures can help us to achieve the different kinds of images we want.
    Canon 80D|Panasonic LX3/LX5
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    Default Re: Optimal F-Stop for Canon Lens

    Quote Originally Posted by jklo
    Thanks!

    Another question I have is when do we want to use a high f-stop (i.e. f16-32), since the DOF will be quite large, requires lots of light, and it is not necessary the sharpest f-stop of the lens.
    Usually this high f-stop will be used when if taking landscapes, macros, and on very sunny days. There's this rule which talks about sunny f/16 and f/22 rules on such occassions...very useful.
    Canon EOS 5D, 24-70 f/4 L IS, 50 f/1.2 L, 70-300 f/4-5.6 L IS, 600EX-RT. Sigma 12-24 f/4.5-5.6 EX.

  10. #10
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    Default Re: Optimal F-Stop for Canon Lens

    try f6.3 on the kit lens.
    For the f2.8 lenses, most of their sweet spots are 2 stops above their max apperture.

  11. #11

    Default Re: Optimal F-Stop for Canon Lens

    Quote Originally Posted by Denosha
    It varies from lens to lens but F8 is normally the sweet spot for most lenses. Anything more than F16 is generally bad though. One way to find out the sweet spot of your lens is to look at reviews like over at http://www.photozone.de/. However, i would take his test results with a grain of salt since he seems to have had quite a bit of variations in some of the lenses he has tested before. Anyway, don't worry too much about always using "sharpest" aperture value but rather more about how it affects the DOF/exposure (and thus the effect you're going for).
    Hi there, just wondering why anything more than F16 is bad? Shudn't the image be even sharper like that? (the only disadvantage I could think of is that a longer shutter speed is required.)

  12. #12

    Default Re: Optimal F-Stop for Canon Lens

    Quote Originally Posted by kelccm
    I think there is too much preoccupation with the optimal f-stop or sharpest aperture. Rather I feel we should concentrate on how using various apertures can help us to achieve the different kinds of images we want.


    especially for those who are new to photography, this pre-occupation with optimal f-stop, optimal speed, optimal camera settings, optimal focal length, optimal camera set up, optimal angle to shoot, optimal composition, and optimal this and optimal that ... there is never much interest in creativity, specifically, let the creative juices flow.

    I wonder if the current generation of photographers would know what to do, just not too far in the past, where we shot with only one lens and it's not a zoom.
    deadpoet
    my portfolio

  13. #13

    Default Re: Optimal F-Stop for Canon Lens

    Galen Rowell the famous mountain photographer used to say " f8 and be there". So there is not much to learn. Just take any lens set to f8 and go anywhere to shoot.
    http://singaporephoto.blogspot.com

  14. #14

    Smile Re: Optimal F-Stop for Canon Lens

    Quote Originally Posted by Deadpoet


    especially for those who are new to photography, this pre-occupation with optimal f-stop, optimal speed, optimal camera settings, optimal focal length, optimal camera set up, optimal angle to shoot, optimal composition, and optimal this and optimal that ... there is never much interest in creativity, specifically, let the creative juices flow.

    I wonder if the current generation of photographers would know what to do, just not too far in the past, where we shot with only one lens and it's not a zoom.
    I couldnt agree more. Im was a newbie b4, now can consider an older newbie , and most of the we get our info from websites that are filled with numbers and tech reviews. Nothing wrong with those, except they serve to detail the instruments.

    Feel that I was too pre-occupied with the details, and numbers to the point where my shots appear technically correct, but still wrong.

    Thankfully many good shooters around me, including those from CS pointed out its more crucial to "see" the image and then decide how to achieve it (pre+post process), than to have a list of best figures, and then apply the shot to them.

    Well just my 2 cents of exp. One thing i really enjoyed about photography is there is always something new to uncover, something new to learn, and heheh more mistakes to make

  15. #15

    Default Re: Optimal F-Stop for Canon Lens

    Seriously the modern lens are so much better than the older ones. So dont worry about the lens but what u can do with them. No one will critique the sharpness n other technical aspects before they critque the picture subject.

  16. #16

    Default Re: Optimal F-Stop for Canon Lens

    Quote Originally Posted by asturias105
    Hi there, just wondering why anything more than F16 is bad? Shudn't the image be even sharper like that? (the only disadvantage I could think of is that a longer shutter speed is required.)
    Because of the diffraction of light. I'm no physicist so here's the definition from this FAQ:

    <Quote>
    Q21. What is diffraction?

    A. When a beam of light passes through any aperture it spreads out.
    This effect limits how sharp a lens can possibly be.

    The diffraction is caused by the limiting of the beam to the size of
    the aperture, not primarily by sharp edges of the aperture. Even if
    one made a "soft edged" aperture that faded slowly from clear to
    opaque, there would still be diffraction, and the size of the central
    part of the diffraction pattern would not change much compared with
    the sharp-edged case.
    </Quote>

  17. #17

    Default Re: Optimal F-Stop for Canon Lens

    Hi! Thank you all for the advice.
    Will keep them in mind, esp about using different apertures to create different effects and the focus on being creative

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