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Hyperfocal distance: a few considerations

Discussion in 'Open Discussion' started by Klorenzo, Oct 4, 2014.

  1. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    I recently took a few pictures at f11/f14 to be sure to have enough DOF and I just spent some time fiddling here:


    to verify if this small apertures were really needed. Here is what I found, mostly related to landscapes.

    At 12mm/5.6 the hyperfocal distance is 1.7 meters and the near limit is 0.9 meters. This means that unless I want something closer than one meter in focus(!) I can just not care about the focus: just avoid to focus on my feet and I should be ok. Event at 2.8 the near limit is 1.7 (focusing right behind the hyperfocal distance). And even if I focus at 20km the near limit at 5.6 does not go behind 1.7 meters.
    I also suppose that if a rock in the foreground is just outside of the near limit it is not going to blur that much.

    At 25mm/5.6 the hyperfocal distance is 7.4 meters with the near limit al 3.7. This again means that for most (landscapes) pictures I just need to set the focus behind 7 meters. Here I could have some close elements in the pictures (grass, rocks, a tree) so going to f8 and focusing at 5 meters gives a near limit of 2.6 meters. f11 gets me a near limit of 1.9 meters. A lot.

    At 40mm/5.6 the hyperfocal distance is 19 meters and we have 9.5 meters of near limit. f8 can push it down to 6.7 meters, f11 to 4.7, f16 to 3.4 meters.

    Summing up: with the 12-40, shooting at 5.6, I do not need to worry about focus unless I have really close elements in the foreground, especially on the long end of the lens. F5.6 or f8 should be good enough, avoiding most of diffraction too.

    Am I simplifying too much?

    I have read this:


    so I know that I am simplifying a little (it explains why and when can be better to focus behind the hyperfocal distance).
  2. lightmonkey

    lightmonkey Mu-43 Veteran

    Dec 22, 2013
    keyword for hyperfocal range is "acceptably sharp"
  3. kwalsh

    kwalsh Mu-43 Top Veteran Subscribing Member

    Mar 3, 2012
    Baltimore, MD
    As lightmonkey said, the issue is "acceptably sharp". Standard DoF tables and calculators are based on viewing a image from a distance the same as the length of its diagonal. In other words viewing a 8x10 print from about 13 inches away. Based on that assumption and the visual acuity of the human eye they come up with a CoC from which they compute the table. This CoC is *vastly* different from what you will see at 100% on your monitor.

    For example, the site you link to uses a CoC of 0.015mm which is between four and five pixels in diameter for a 16MP m43 sensor. So the area of that blur disk will cover around twenty pixels on the sensor. That means at the edges of the DoF you will be producing an image with a resolution of about 1MP.

    I'm guessing you didn't buy the rather expensive and beautiful 12-40/2.8 to produce 1MP images ;) 

    Run your numbers again using a CoC of 0.005mm and you'll have a better idea of the DoF you get when using a table properly calculated to achieve the resolutions digital shooters consider "acceptable" when examining at high magnification.

    As to dialing the aperture to get more DoF you'll find a lens as sharp as the 12-40/2.8 will begin to visibly lose resolution to diffraction past about F/8 and when viewed at 200% even by F/5.6. I consider shooting past F/8 to be an emergency situation and if I can will focus stack instead. Although obviously if the situation doesn't allow for focus stacking and you need to go to F/11 and F/16 then do it as slight loss of resolution is better than out of focus!
    • Like Like x 3
  4. imahawki

    imahawki Mu-43 Veteran

    Aug 12, 2014
    This is very instructive considering I just had situation where I inadvertently took some group shots with too shallow DOF. It seems like f/4 or f/5.6 is a good backup aperture considering the working distances I'll normally be using in those situations.
  5. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Thanks for the answers. I repeated the tests with 0.005 CoC (you can find it at the bottom of the Cameras dropdown) and here is the number comparison (f5.6):

    near limit (Hyp distance) before after max near limit (after)
    12mm 0.9 (1.7) 2.6 (5.1) 5
    25mm 3.7 (7.4) 11.1 (22.1) 22
    40mm 9.5 (19) 28 (56) 56

    quite different (exactly three times, the inverse of the CoC difference). At 12mm it is still easy, you can also use 2.8 "leaving out" just 5 meters in front of you. With "max near limit" I mean the maximum distance you can get for the near limit when you push the focus far into the scene. I think it is not a coincidence that it is the same as the hyperfocal distance (HD). Another thing I noticed is that at the HD the near limit is always half the HD.
    Putting the two together means that you can place the near plane anywhere between half HD and HD from you. Put it closer and you start to loose focus (at the chosen CoC) on the far end.

    At 12mm even f4 could be an easy "default" aperture. After 25 can be tricky with elements in the foreground but I think 5.6 or 8 should be enough. I'm talking about casual handheld shooting.

    Here are a couple of the images that started this thread:

    Subscribe to see EXIF info for this image (if available)

    Subscribe to see EXIF info for this image (if available)

    Considering that these are compressed, resized jpeg the elements in the foreground are not that bad. They are overall a little soft, maybe it is the raw processing or the lens (14-42 EZ) or diffraction. Or a hurried photographer.
    • Like Like x 1
  6. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    So, you're forgetting one thing. The foreground is also at the edge of the frame. You're using a lens that is sharper in the centre and softer at the edges. That has an effect too. If you want sharp to the edges with acceptable DOF all the way as well, you're going to have to use a lens which is sharp across the whole frame as well as making sure that your foreground and horizon both fall within the limits of your depth of field. The 14-42 is not such a lens.
  7. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    One more reason not to use super small apertures to get the foreground in proper focus: even if I get one more meter in better focus the lens is not going to pick it up well enough.
    Even with the 12-40 I wont bother to go to f8, f11 or even f14 as I did last time, except to make a few more experiments.
    • Like Like x 1
  8. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    Acceptable is acceptable. The original coc is still a usable guide. Requiring sharpness when pixel peeping is a sign of losing focus on the objective.
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