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Hyperfocal Distance

Put simply, one uses the hyperfocal distance to determine what distance to focus a camera to achieve the greatest depth of field. Technically, hyperfocal distance refers to the distance from a camera such that if the camera is focused at that distance, everything from infinity to halfway between the camera and that distance is in focus. The hyperfocal distance is used to achieve pan focus (everything in the image in focus).

The hyperfocal distance depends on the [[Photography:Glossary#Focal Length|focal length] of the lens, the f-stop and resolution of the sensor/film. The resolution is used to control how sharp the image needs to be for it to be considered "in focus". For a particular digitial camera, it can be considered constant.

Here is the formula to calculate hyperfocal distance:

Image:hyperfocaldistanceformula.png

where H is the hyperfocal distance, f is the focal length of the lens, (for digital cameras, use the actual focal length), N is the f-stop, and C is the cirle of confusion (this controls how "in focus" something has to be). The unit of measurement (mm, feet, etc) of the hyperfocal distance is determined by the unit of the focal length. As focal length is usually measured in millimeters, then the hyperfocal distance will also be in millimeters.

For my D70 (a 6 mega pixel camera), C is 0.02.

As you can see, the smaller the aperture (thus larger f-stop), the closer the hyperfocal distance. As well, the shorter the focal length, the closer the hyperfocal distance. This gives the first tips for achieving your desired hyperfocal distance:

  • Use a wide angle lens
  • Use a small aperture

Small apertures mean slower shutter speeds, so you may want to bring a tripod.

Taking image with pan focus is one of the best uses of wide angle lenses.

This page has an online hyperfocal distance calculator and downloadable charts that can be printed.

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How to use Hyperfocal distance

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  1. The best way to start is to determine the smallest aperture (thus the largest f-stop) such that the shutter speed is fast enough for you to hold the camera steady. If you have tripod, then you are probably fine to use just about any shutter speed, barring other considerations, such as blur due to motion. If you are hand holding, the 1/30s is probably safe, however if you think you can go slower, then by all means give it a try.
  2. Lookup the hyperfocal distance on the chart using the focal length and aperture you've chosen. Divide the hyperfocal distance in half. This is the closest any object can be and still be in focus.
  3. Find the closest object you want in focus. If it is closer than the distance calculated in step 2, then you need to adjust your settings. Either decrease the aperture size, or move the camera further away. If the closest object is further away than the distance from step 2, see if you can use a larger aperture. By doing so, you reduce the risk of losing sharpness due to diffraction.
  4. Now that you have your settings dialed in, take the picture. If you are using digital, take a bunch.

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