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F Stop.............!!

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  • F Stop.............!!

    https://e-group.uk.net/forum/showthr...highlight=Mans

    The comment was that my f stop was 7.1, and that MFT photos show diffraction..

    I would say that you probably didn't need to go to f/7.1 though so - maybe f/5.6 and you could have enjoyed a faster shutter speed or a lower ISO setting.

    One thing all Micro/Four Thirds users should remember is that past f/5.6 you start to lose resolution due to diffraction.

    On the other hand, using a high ISO also has the same effect - whether or not these two factors are mutually exclusive or cumulative; that's a good question and needs answering!
    Mark Johnson

    My Sailing Page

    My Flickr

  • #2
    Re: F Stop.............!!

    Your picture doesn't look unduly soft to me,I'm a little more sceptical about the wisdom.
    I've had some shots that apparently "look soft because of defraction" using extension rings for pictures of model cars.
    I was stopped down as far as possible to get depth of focus front to back.
    Is it soft? I was happy enough but I didn't run through a selection of F numbers to get the widest aperture with the car in focus, I used the "wisdom" that a higher F number would result in greater DoF




    Volkswagen Golf by AMc UK
    Porsche at Le Mans by AMc UK, on Flickr

    According to EXIF in Flickr both our shots were taken "Exposure Mode - Auto". I usually use Program unless I'm specifically choosing an aperture or shutter speed for effect.
    Do you know what mode you were in and why you were at those settings?
    https://www.flickr.com/photos/amcuk/

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    • #3
      Re: F Stop.............!!

      Diffraction can be numerically estimated using the Rayleigh criterion for the size of the Airy disk. For closely-spaced objects this approximates to:

      x = 2.44 L N

      where:

      x = size of Airy disk diameter
      L = wavelength of light
      N = f-stop

      Plugging this in for green light (in the middle) and f7.1, we get:

      x = 0.009mm

      This is still much smaller than the usual circle of confusion used for DoF calculations (0.015mm). In other words, at f7.1, diffraction is not a significant factor.

      We don't get an Airy disk larger than the circle of confusion until about f11.

      In other words, up to f11 you're fine in practical terms, although if you nit-pick, keep it at f5.6 and below.
      Paul
      E-M1ii, Pen-F and too many lenses
      flickr
      Portfolio Site
      Instagram

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      • #4
        Re: F Stop.............!!

        Diffraction limiting of sharpness is a complex subject that depends on many factors, including pixel size and how the image is viewed. There are some calculations on the 'Cambridge in Colour' website that illustrate these points.

        For example, the 'simple' calculator at https://www.cambridgeincolour.com/tu...hotography.htm suggests that an MFT camera becomes 'diffraction limited' at smaller openings than f/11 (Olympus now quote this figure also) This, however, assumes that you are viewing a 10"x8" print from 1 foot away.

        The calculator in Part 2 of the article at https://www.cambridgeincolour.com/tu...tography-2.htm considers more aspects of image quality and suggests that diffraction effects can become visible at wider openings. For example, an MFT camera with 20MP sensor may show some 'effects' at openings smaller than f/5.2

        In my own experience, i have found that using 'stacking' for macro photography, with my 60mm lens set at f/2.8, shows better micro-contrast than when set at f/8. I now use wider apertures whenever possible and rely on 'stacking' to increase the apparent depth of field.
        Mike
        visit my Natural History Photos website:
        http://www.botanicdesign.co.uk/Natur...story/home.htm

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        • #5
          Re: F Stop.............!!

          Yes, stacking is a great technique and better than stopping down for most things - but of course you need a relatively stable platform for it. I took this yesterday with the 8mm fisheye. Wide open at f1.8 and 15 shots:


          Schrooms by Paul Kaye, on Flickr
          Paul
          E-M1ii, Pen-F and too many lenses
          flickr
          Portfolio Site
          Instagram

          Comment


          • #6
            Re: F Stop.............!!

            Super shot, Paul - I've never thought of stacking fish-eye shots
            Mike
            visit my Natural History Photos website:
            http://www.botanicdesign.co.uk/Natur...story/home.htm

            Comment


            • #7
              Re: F Stop.............!!

              Do you know what mode you were in and why you were at those settings?
              Yes I was in Auto Mode onC1 with several other settings.

              Why??

              My simple rule is that in summer I use a higher stop a there is likely to be more light and Dof benefits. The 12-40 pro just gives and gives. Alas I do get forgetful and in my excitement forgot to open up the aperture. But I think the resulting photo did ok despite me. 👹
              Mark Johnson

              My Sailing Page

              My Flickr

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              • #8
                Re: F Stop.............!!

                Just curious as to why you’d got the settings you had.
                As I said I normally shoot P and scroll from there if needed.
                Some of my odder results have been inadvertently leaving A or S mode settings and moving on to another subject.
                As long as you’re happy with the image it’s all academic really anyway.
                https://www.flickr.com/photos/amcuk/

                Comment


                • #9
                  Re: F Stop.............!!

                  Just to be clear, I didn't say the shot wasn't sharp but seeing as the shutter speed was quite slow I didn't really think such a small f-stop made sense. DOF wasn't an issue with the composition. I've seen other shots from different photographers that were definitely over-stopped down for no apparent reason and diffraction softness was evident.

                  Ian
                  Founder and editor of:
                  Olympus UK E-System User Group (http://e-group.uk.net)
                  Four Thirds User (http://fourthirds-user.com)
                  Digital Photography Now (http://dpnow.com)
                  Olympus camera, lens, and accessory hire (http://e-group.uk.net/hire)

                  Twitter: www.twitter.com/ian_burley
                  Flickr: www.flickr.com/photos/dpnow/
                  Pinterest: www.pinterest.com/ianburley/
                  NEW: My personal BLOG ianburley.com
                  sigpic

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                  • #10
                    Re: F Stop.............!!

                    My experience with several camera club members who have added or switched to m4/3 from FF gear is that they keep their old habits at first, and don’t take advantage of the dof advantages of the smaller sensor. This results in high ISOs and slow shutter speeds, and not surprisingly they start to moan about their decision.

                    Telling them to open up by 2 stops comes as a complete revelation.

                    The second lesson is about Exposing to the Right.

                    So far I’ve never had anyone still complain after that ;-)
                    Regards,
                    Mark

                    ------------------------------
                    http://www.microcontrast.com
                    Too much Oly gear.
                    Panasonic GM5, 12-32, 12-35, 15. Laowa 7.5.
                    Assorted legacy lenses, plus a Fuji X70 & a Sony A7S.

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                    • #11
                      Re: F Stop.............!!

                      Originally posted by drmarkf View Post
                      My experience with several camera club members who have added or switched to m4/3 from FF gear is that they keep their old habits at first,
                      Mark Johnson

                      My Sailing Page

                      My Flickr

                      Comment


                      • #12
                        Re: F Stop.............!!



                        Peacock butterfly taken with an f22 aperture! (Not on purpose,,:-))….F22 1/200 sec and ISO 6400

                        Whilst its not the best photo I have ever taken, the quality is I guess only just OK. Where is the refraction/defraction that the small aperture is giving....

                        The high ISO kinda knackers the resolution...………….
                        Mark Johnson

                        My Sailing Page

                        My Flickr

                        Comment


                        • #13
                          Re: F Stop.............!!

                          Mark Johnson

                          My Sailing Page

                          My Flickr

                          Comment


                          • #14
                            Re: F Stop.............!!

                            For sure, but getting them past first base by knowing where 'equivalence' lies in that area makes a huge difference, otherwise m4/3 has one arm tied behind its back.
                            Regards,
                            Mark

                            ------------------------------
                            http://www.microcontrast.com
                            Too much Oly gear.
                            Panasonic GM5, 12-32, 12-35, 15. Laowa 7.5.
                            Assorted legacy lenses, plus a Fuji X70 & a Sony A7S.

                            Comment


                            • #15
                              Re: F Stop.............!!

                              Hi
                              So having just purchased an Olympus om-d e-m1 mkii, with thoughts of changing to MFT, I am now wondering if it was the right move.
                              I have a Canon EOS R and do not seem to have this issue with DOF, the smaller the aperture the better dof and detail, as far as I can see.
                              Am I confused here?
                              Roy

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