Announcement

Collapse

December's CHALLENGE

The topic to inspire your creative juices this month is BOXES Please don't forget to vote on November's LEAVES challenge and please re-vote if you already did but before the recent forum upgrade.

See more
See less

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

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Re: F Stop.............!!

    Originally posted by royd63uk View Post
    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
    Diffraction affects all lenses when they are stopped down too far. With FF you can stop down more before the effects are apparent.

    But remember you don't need to stop down as much on (Micro) Four Thirds to achieve the desired depth of field.

    It's simply a matter of scale.

    Also, in the old days there was often a necessity to stop down in order to achieve optimum lens sharpness, but modern lenses are now very sharp wide open.

    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

    Comment


    • #17
      Re: F Stop.............!!

      But remember you don't need to stop down as much on (Micro) Four Thirds to achieve the desired depth of field.
      Thats was one of the questions i was going to ask.

      So one of my favourite f stops on full frame was F8, so would 5.6 on MFT work the same?
      Roy

      Comment


      • #18
        Re: F Stop.............!!

        The only thing that works the same as f/8 on "full frame" is f/8 on full frame The whole thing is a combination of focal length, sensor size and aperture, they all work together. As a very rough guide, I think the idea is that if you want to match a 100mm lens at f/8 on FF, you can use a 50mm lens at f/4 on MFT. This will give roughly the same field of view and depth of field. But even that is approximation, the best bet is to use it as a starting point and see how it works in your circumstances.

        John
        Last edited by Bikie John; 7th August 2019, 04:24 PM. Reason: Add formatting

        Comment


        • #19
          Re: F Stop.............!!

          Originally posted by royd63uk View Post
          Thats was one of the questions i was going to ask.

          So one of my favourite f stops on full frame was F8, so would 5.6 on MFT work the same?
          Roy
          You basically halve the number so f/4 is equivalent to f/8.

          A very handy benefit is that you get greater brightness for the same DOF and so the benefit of faster shutter speed and/or lower ISO options.

          What I mean is that the brightness at f/8 is the same regardless of sensor size/format (given the same subject).

          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

          Comment


          • #20
            Re: F Stop.............!!

            Originally posted by pdk42 View Post
            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.
            That's useful information Paul, thank you.

            Does the above apply equally to all focal lengths? And does diffraction effect film in the same way that it effects digital sensors? (Obviously film provides a bigger 'sensor' in most cases.)
            ---------------

            Naughty Nigel


            Difficult is worth doing

            Comment


            • #21
              Re: F Stop.............!!

              Originally posted by Naughty Nigel View Post
              That's useful information Paul, thank you.

              Does the above apply equally to all focal lengths? And does diffraction effect film in the same way that it effects digital sensors? (Obviously film provides a bigger 'sensor' in most cases.)
              Film is different because there are no photosites on the surface of film emulsion.

              I can't if there is a comparable effect but it's certainly not the same.

              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

              Comment


              • #22
                Re: F Stop.............!!

                Originally posted by Ian View Post
                Film is different because there are no photosites on the surface of film emulsion.

                I can't if there is a comparable effect but it's certainly not the same.

                Ian
                I may be wrong, but a film is less likely to suffer from diffraction as the emulsion grains have an element of randomness to them, so the diffraction patterns that can be seen are less likely to occur. A sensor is very regular and precise in its construction so diffraction patterns are more likely.

                Or something?
                I didn’t get where I am today....

                Comment


                • #23
                  Re: F Stop.............!!

                  Originally posted by Walti View Post
                  I may be wrong, but a film is less likely to suffer from diffraction as the emulsion grains have an element of randomness to them, so the diffraction patterns that can be seen are less likely to occur. A sensor is very regular and precise in its construction so diffraction patterns are more likely.

                  Or something?
                  I'm sure that's a factor but the primary one is the size of the photosites (basically holes in the surface of the sensor) on the sensor surface in relation to the airy discs.

                  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

                  Comment


                  • #24
                    Re: F Stop.............!!

                    I suspect that a lot of current lenses were designed to give optimum performance at the wider apertures.

                    In film days, lenses were designed to be best at around f8 or f11. My Kiron 105 has the f16 marked in blue and the handbook says to use it for macro.

                    My default aperture for macro at all magnifications is f11 but I may use f8 for a shallow subject. At the higher magnifications I remove diffraction digitally.

                    Harold
                    The body is willing but the mind is weak.

                    Comment

                    Working...
                    X