Depth of field – what it is and how to use it

Put simply depth of field  how much of your picture – foreground to background – is sharp and in focus.  But how can you control and use it to take expert shots?

depth_of_fieldLet me explain …

When you focus your camera lens on a point everything else will not appear equally sharp.

This decline in sharpness is gradual.  And there’s a zone behind and in front of what you’re focused on that looks sharp (there blur’s there, it’s just too small for your eyes to see).  This zone is known as the depth of field.

The extent of the depth of field depends on how great a degree of blur you’re prepared to accept.  And – in turn –  this depends on the final print enlargement.The depth of field also depends on the aperture, the focal length and distance from the lens to the subject.To help you many digital SLR cameras have a depth of field preview.  This allows you to see the depth of field before you shoot.Here are two examples:

To isolate a subject from the background: Use a large aperture (ƒ1.4 – ƒ 4) for a small depth of field (this is called selective focus).

To isolate a subject from the background: Use a large aperture (ƒ1.4 – ƒ 4) for a small depth of field (this is called selective focus).

To gain best overall sharpness: Use a small aperture (ƒ11 – ƒ 16) and a wide-angle lens, preferably set to the hyperfocal distance.

To gain best overall sharpness: Use a small aperture (ƒ11 – ƒ 16) and a wide-angle lens, preferably set to the hyperfocal distance.

Here’s some takeaways:

  • ‘The bigger the f-number … the smaller the aperture … the greater the depth of field’
  • All else being equal, shorter focal lengths provide greater depth of field.
  • The closer the subject, the smaller the depth of field.
  • The luminous, soft out-of-focus areas produced by fast lenses are called ‘bokeh’.
  1. Thanks, It’s good to remember the basics every now and again.

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