Focus – In Focus Throughout

Keeping everything in focus from the camera out to infinity

NOT ENTIRELY POSSIBLE – But we can come close (enough)

This may be the most technical of all the lessons. Please bear with me and try to understand it – or at least the concepts. You must understand the previous lesson topic first.

The secret to focus throughout is something called Hyperfocal Distance (HFD). The simplest explanation is (follow the previous link if you doubt me or are a masochist) –

HFD is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp

In other words, HFD is the focus distance with the maximum depth of field

When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp

For concreteness, assume the HFD is 6 feet (how we know the actual HFD comes later). The HFD explanation above tells us –

Everything from 3 feet to infinity will be acceptably sharp; the DOF can’t be any greater; if you need something inside of 3 feet in focus – change your position or try stopping the lens down (use higher f-number)

We won’t dwell on the exact definition of  acceptably sharp except to note that it depends on things (among others) such as

Size of the print to be made from the image

Print viewing distance

Viewer’s eyesight (20/20?)

Whether using the exact HFD is important (or even practical) depends on the image’s intended purpose

Often it’s not worth sweating the details; understanding HFD & DOF basics can get us close enough

HFD is useful for landscapes but not even desirable for photos like the inauguration photo example in lesson #1a

Thoughts about “the details” –

  • If you know the HFD is 6 feet, how will you be able to focus at precisely 6 feet? Tape measure? Use the lens distance scale (it’s not accurate enough)? Guesstimate?
  • If you know the HFD is 6 feet and cannot set a precise focal distance on your camera, what are the consequences?
  • Consequences – As long as you focus at a distance greater than the correct HFD, the worst that will happen is that some of the DOF between you and the correct HFD distance will be lost. In our HFD = 6′ example, in the worst case of setting your focus distance to infinity, your DOF would be 6′ to infinity instead of 3′ to infinity. Whether this 3 foot loss is a deal breaker or not depends on the importance of your foreground.
  • The important thing to remember is – if you know the HFD and ensure that your focal distance is set to at least that far you’re guaranteed that the DOF will extend from the correct HFD distance to infinity.

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The $64,000 Question, how do we determine HFD? Unfortunately the answer is not – “It’s simple“. HFD depends on three things (plus a chart) –

  1. The focal length of your lens- actual and not multiplied by 1.5 (Nikon) or 1.6 (Canon) or whatever
  2. The f/stop you’re using
  3. The Circle of Confusion (CoC – another masochist’s link)) which is camera dependent
  • 35mm = 0.030, Nikon 1.5X = 0.020, Canon 1.6x = 0.019
  • Other cameras – find it HERE

With these three values we use a chart to find HFD (do you see why the practicality of this in the field might be an issue? If you have an iPhone, there’s an HFD “app”).

This chart shows that for a 50mm lens at f/16 (CoC = 0.030) the HFD is 17 feet. If our focus distance is set to 17 feet (your camera is set to Aperture Priority & Manual Focus isn’t it?) everything from 8.5 feet (1/2 of 17) to infinity will be in focus.

A download for a program to create and print an HFD Chart to match your needs can be found here at DOFMaster (source of the above chart). For additional DOF related tools see the DOFMaster main site. For articles on DOF & HFD check out this portion of DOFMaster (may be more than you want to know).

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Assignment – Download the HFD program and use it to print an HFD chart (the part unique to you will be the CoC for your specific camera). Go outside with your camera & the chart and experiment (you can’t learn to use your camera just by reading).

Need some ideas? – Go to the  golf course. Find a prominent foreground element on a long hole (you want something both near & far since that’s the whole idea of what we’re trying to learn). The hole’s distance marker makes a good foreground element; move a distance away from it equal to the HFD and start from there.

NOW experiment – 1) focus short of the HFD such as at your lens’s minimum focal distance; the distant objects should be out of focus in the resulting capture, 2) focus at the HFD , 3) focus beyond the HFD such as infinity where the hole marker should be still in focus but everything short of that won’t be; use different focal lengths (wide, normal & long) and different f/stops (wide open, f/8 or 11, f/22).

Try to predict the results of these experiments by looking at the chart. The more you experiment, the more you’ll learn – it’s up to you alone. Here are some HH Golf Course examples from my personal archive. Try shots like these and experiment with different settings to see what happens. Click on a thumbnail to enlarge.

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In the next topic we’ll consider how what we’ve covered thus far might allow us to make creative images – the whole point of this course. Until then, here are few example from my personal archive that illustrate cases where HFD was important – they all have a foreground that needed to be sharp (as well as the “far-ground”)

5 thoughts on “Focus – In Focus Throughout

  1. This really highlights the DOF differences for short vs long focal length lenses! – Mike Weppner

    • I assume you mean the HFD chart – yes, indeed. The effect of stopping down (higher f/stop number) is *almost* as good – but not quite. The trade-offs involve shutter speed (and an image quality factor called diffraction which worsens as you stop down).

      I own a 12-24 and a 16-50 and they are wonderful when a large DOF is needed.

  2. That is what I meant … I considered using 35mm, 50mm and 100mm for the exercise … stopped at 70mm to keep distances reasonable for the situation.

    Recently got a 12-24, and this lesson really emphasized the benefits.

    Thanks, Mike Weppner

  3. I have been attempting to understand HFD. My beginner’s problem/hold up was assuming the CoC was associated with my lens (Tamron 28-300) rather than my camera (Canon EOS 20D). Finally, after reading numerous articles I found one that has an illustration of the CoC and there it was in the camera! So have attained a number of 0.019. Now can perform the HFD calcs.

    http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

    Somewhat embarassing but I am learning what I dont know and this is the whole point of this course.

    I have had no success downdoading the HFD chart yu suggested. As noted in their instructions if any problem occurs contact them to provide an email download, I have, but no response from them after 3 days.

    Also have been experimenting and learning regarding DOF but nothing worth posting.

    • Russ,

      Regarding the CoC, I stated it plainly(I thought) under the item labeled $64000? Here is what I wrote (note the reference to CAMERA and not lens; it even includes the 0.019 you ultimately found for your Canon) –
      ________________>>

      3. The Circle of Confusion (CoC – another masochist’s link)) which is camera dependent

      * 35mm = 0.030, Nikon 1.5X = 0.020, Canon 1.6x = 0.019
      * Other cameras – find it HERE
      ________________<< Note that HERE (the final word) was a link to a site that listed your camera. I tried to help everyone avoid having to search laboriously on their own – by either choosing the 0.020 Nikon or 0.019 Canon values that I cited or simply clicking on the link. Don’t know what else I could have done 😉

      As for the download problem – Nothing would download at all??? What *exactly* was the nature of the problem (you did x and y happened)? It worked fine here & for another participant. It's the leading site worldwide on the subject & has been around for ages so it isn't likely an error that they missed.

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