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True Hyperfocal Distance

If you are photographing compositions that require depth of field, then you must focus your camera at the hyperfocal distance to achieve the most amount of sharpness for elements in the foreground and background.  There are copious amounts of information on the internet regarding hyperfocal distance, however most sources are very confusing and bogged down in technical jargon.  Some sources also use outdated mathematical models that use formulas to compute the hyperfocal distance, and when using these methods the calculated hyperfocal distance is inaccurate, resulting in photos that are mediocre/inadequate at best!  I will describe what hyperfocal distance is and how to properly use this concept in the field to produce sharper photos by obtaining the greatest depth of field.

 

The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp; that 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.  See the illustration below.

The concept of hyperfocal distance is easy to understand: focus a lens at the hyperfocal distance and everything in the photograph from some near distance to infinity will be sharp. Landscape photographs are often taken with the lens focused at the hyperfocal distance - near and distant objects are sharp in the photos.

 

The hyperfocal distance is easier to understand when applying real world examples.  The methods I will describe have been proved mathematically.  Please see notes below for more information.  Also, I have proven in the field with my own camera that the older hyperfocal distance models are obsolete.  Let's continue with an example.

 

Once upon a time you were in a mountain valley, with groves of wild flowers in bloom.  You want to capture the flowers close up in the foreground, with the lake behind the field of flowers, and the mountains in the far distance and on either side of the valley.  You are standing 1.5ft away from the flowers, and you want everything from the flowers to the mountains in focus.  The focusing distance is 1.5ft.  Focusing distance is very intuitive – by using auto focus or manual focus, focus the camera on the most important element in the foreground.  Whatever distance the camera's Rangefinder indicates = the focusing distance.  In our example, focus on the flower petals that are 1.5ft away.  When acquiring depth of field, 95% of the time you will choose a focal point that is at the very bottom of the frame.  This is because we are trying to get everything in sharp focus, from front to back.

 

After knowing what the focusing distance is, you need to consult a special chart that will tell you what aperture to use.  This chart can be downloaded here.  To use the chart, we need to know two things. 1) What is the focusing distance?  2) what is the focal length of the photo you are attempting to take?  We have already figured out the focusing distance at 1.5ft.  To find the focal length, simply look at your camera lens and read what "mm" the barrel is set to.  Let's say for the photo in the mountain valley you compose the photo with 16mm focal length.

Chart 1.0

Use Chart 1.0 above and find 16mm at the top.  All numbers listed in the body of the spreadsheet are quoted in feet.  Also, all numbers listed in the body of the chart are hyperfocal distances!  Since our focusing distance is 1.5ft, scroll down the 16mm column until you find the first hyperfocal distance number that is slightly below the focusing distance.  The entry that meets our criteria is 1.35 – the hyperfocal distance is 1.35ft.  Now look to the left of this entry and we find the required aperture to use.  For our example, f22 is the correct aperture to use to ensure sharp focus from foreground to background.  This method does not require you to change the focusing distance to 1.35ft.  In our example, leave the focusing distance at 1.5ft and use f22 for the aperture.

 

Seems easy right?  Be careful, there are caveats!  The biggest being that most new manufactured lenses do not have sophisticated rangefinders, meaning the range in feet annotated on the lens is not very descriptive.  For instance, I own a Nikon 16-35mm and the rangefinder measurements are annotated 1 ft, 1.25ft, 2ft, and ‘infinity'.  The lens has the ability of focusing closer than 1 ft, and can focus between 2ft and infinity.  The problem is when I focus on something between 2ft and infinity, I will have to guess at what focusing distance to use, since there are no focusing distances annotated on the lens.  I've tested the lens rangefinder and found different focusing distances on the lens at 2.5ft up to 20ft.  The best way around this is by guessing!  I know some of you readers won't like hearing that, but unless you want to spend $100+ dollars on a laser sight measurement tool, guessing is your only answer.  Besides, it turns out that guessing doesn't really make much noticeable difference anyway, as long as your guess is not totally wrong!  If your lens rangefinder measures your focusing distance at a distance that is not annotated on your lens, estimate approximately how far away you are from your spot of focus and use that as the focusing distance.  Then simply use the method I described above to track the correct hyperfocal distance and aperture.

 

Another major caveat is composing the photo at larger focal lengths e.g. 28mm, 35mm, 50mm.  By consulting Chart 1.0 we see that at 35mm, when using f22 the hyperfocal distance is 6.34ft.  Now let's use the mountain valley example again where our intention is to focus on flowers using a focusing distance of 1.5ft.  The focusing distance is lower than the hyperfocal distance!  This means that if you take the photo with the current camera settings, you will not achieve sharpness from front to back.  The foreground of flowers will be sharp because you are focusing directly at them, however the mountains in the background will be out of focus and blurry.

 

So how do you fix this?  The problem is you can't!  You must make sacrifices.  There are two potential remedies. 1) focus the lens anywhere from 1.5ft - 6.34ft.  2) recompose the photo.  The first choice: if you manually refocus the lens at 6.34ft, everything from 3.17ft to infinity will be in sharp focus.  However our flowers are 1.5ft away and if you press the shutter while focused at 6.34ft, the flowers will not be 100% sharp.  Therefore, we need to sacrifice by letting the background go slightly unsharp.  Focus the lens closer to 1.5ft, since we want to keep the flowers as sharp as possible.  There is no correct focusing distance to use, rather it is a creative decision made by the photographer which element of the photo will render sharp or unsharp. The second choice: you can physically move the camera back 4.84ft (6.34 – 1.5).  By moving the camera backwards 4.8ft and focusing at the flowers, the focusing distance becomes 6.34ft, which is exactly the same distance as the hyperfocal distance.  At 6.34ft, everything in the foreground and background will be sharp.  However, now the composition has completely changed.  The photographer will have to recompose the photo, and could possibly lose the essence of what attracted them to take the photo in the first place.

 

Since the composition changes with the second choice, I feel it is not the best option, therefore I never utilize it in the field.  I compromise by using the first method and allowing a small area of the photo to go unsharp.  Depending on what elements I choose to intentionally make unsharp dictates my focusing distance.  At 35mm, the hyperfocal distance is much larger than my focusing distance; therefore the aperture is set at f22.  Lowering the aperture will defeat our purpose of getting everything as sharp as possible.  In our example, I will intentionally unsharpen the mountains and sharpen the flowers.  In my opinion, the flowers in this example take precedence over the mountains, and I want to retain as much detail as possible in the flowers.  This is my preference for this example, and is not true at all times and for all situations.  Each potential opportunity is different, and by choosing where to sacrifice sharp details is part of your creative vision!

 

To see examples of my photography that includes many examples of depth of field, please click the link Stefan Hofer Photography : Creative Photography Portfolios

 

For more topics on photography education, please head over to my BLOG!

 

NOTES:

http://www.kenrockwell.com/tech/focus.htm

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