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.
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) –
- The focal length of your lens- actual and not multiplied by 1.5 (Nikon) or 1.6 (Canon) or whatever
- The f/stop you’re using
- 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).
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.
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”)