- HYPERFOCAL DISTANCE -
Focusing your camera at the hyperfocal distance ensures maximum sharpness from half this distance all the way to infinity. The hyperfocal distance is particularly useful in landscape photography, and understanding it will help you maximize sharpness throughout your image by making the most of your the depth of field-- thereby producing a more detailed final print. Knowing it for a given focal length and aperture can be tricky; this section explains how hyperfocal distance is calculated, clears up a few misconceptions, and provides a hyperfocal chart calculator. I do not recommend using this distance "as is," but instead suggest using it as a reference point.
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Note how only the right image has words which are (barely) legible at all distances. Somewhere between the nearest and furthest subject distance lies a focal point which maximizes average sharpness throughout, although this is rarely halfway in between. The hyperfocal distance uses a similar concept, except its bounds are from infinity to half the focus distance (and the amount of softness shown above would be unacceptable).
WHERE IT'S LOCATED
Where is this optimal focusing distance? The hyperfocal distance is defined as the focus distance which places the maximum allowable circle of confusion at infinity. If one were to focus any closer than this--if even by the slightest amount--then at some distance beyond the focal plane there would be an object which is no longer within the depth of field. Alternatively, it is also true that if one focuses at a very distant object on the horizon (~infinity), then the closest distance which is still within the depth of field will also be the hyperfocal distance. To calculate its location precisely, use the hyperfocal chart at the bottom of this page.
The problem with the hyperfocal distance is that objects in the far background (treated as ~infinity) are on the extreme outer edge of the depth of field. These objects therefore barely meet what is defined to be "acceptably sharp." This seriously compromises detail, considering that most people can see features 1/3 the size of those used by most lens manufacturers for their circle of confusion (see "Understanding Depth of Field"). Sharpness at infinity is particularly important for those landscape images that are very background-heavy.
Sharpness can be a useful tool for adding emphasis, but blind use of the hyperfocal distance can neglect regions of a photo which may require more sharpness than others. A finely detailed foreground may demand more sharpness than a hazy background (left). Alternatively, a naturally soft foreground can often afford to sacrifice some softness for the background. Finally, some images work best with a very shallow depth of field (such as portraits), since this can separate foreground objects from an otherwise busy background.
When taking a hand-held photograph, one often has to choose where to allocate the most sharpness (due to aperture and shutter speed limitations). These situations call for quick judgment, and the hyperfocal distance is not always the best option.
RULE OF THUMB FOR FINITE SCENES
What if your scene does not extend all the way to the horizon, or excludes the near foreground? Although the hyperfocal distance no longer applies, there is still an optimal focus distance between the foreground and background.
Many use a rule of thumb which states that you should focus roughly 1/3 of the way into your scene in order to achieve maximum sharpness throughout. I encourage you to ignore such advice since this distance is rarely optimal; the position actually varies with subject distance, aperture and focal length. The fraction of the depth of field which is in front of the focal plane approaches 1/2 for the closest focus distances, and decreases all the way to zero by the time the focus distance reaches the hyperfocal distance. The "1/3 rule of thumb" is correct at just one distance in between these two, but nowhere else. To calculate the location of optimal focus precisely, please use the depth of field calculator. Ensure that both the nearest and furthest distances of acceptable sharpness enclose your scene.
The hyperfocal distance is best implemented when the subject matter extends far into the distance, and if no particular region requires more sharpness than another. Even so, I also suggest either using a more rigorous requirement for "acceptably sharp," or focusing slightly further such that you allocate more sharpness to the background. Manually focus using the distance markers on your lens, or by viewing the distance listed on the LCD screen of your compact digital camera (if present).
You can calculate "acceptably sharp" such that any softness is not perceptible by someone with 20/20 vision, given your expected print size and viewing distance. Just use the hyperfocal chart at the bottom of the page, but instead modify the eyesight parameter from its default value. This will require using a much larger aperture number and/or focusing further away in order to keep the far edge of the depth of field at infinity.
Using too large of an aperture number can be counterproductive since this begins to soften your image due to an effect called "diffraction." This softening is irrespective of an object's location relative to the depth of field, so the maximum sharpness at the focal plane can drop significantly. For 35 mm and other similar SLR cameras, this will become significant beyond about f/16. For compact digital cameras, there is usually no worry since these are often limited to a maximum of f/8.0 or less.
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