Depth of Field - Use It to Create Better Images

You may have noticed the way many professional photographers blur the background and sometimes even the foreground like the above image to create a nice looking image.  In the image above, the foreground and the background are both blurred bringing more attention to the lady in the shot.

Most point and shoot cameras keep the background in focus by default, but many Sony cameras, even the low cost ones, have a DE-FOCUS option which will blur the background giving a nice effect like you see the background above.  However, Cameras with interchangeable lenses give the photographer lots of options for controlling the focus of the image.

Although I did not take the image above (but do have the rights to use it), the photographer likely had the lens nearly wide open, focused on the lady and the lens setting helped both the foreground and background be out of focus.  Many consumer lenses have a 3.5-4.5 widest opening.  The lower the number the smaller amount the depth of field or the more the background or foreground may be out of focus when finding one focal point like the lady above.  Depth of field is also changed by the distance from the subject to the camera and the distance of the subject to the background.  The larger the number, say f/16, means the more the background is likely to be in focus, but there is still a correlation of camera from subject and subject to background.

If you have the ability to either set your camera on DE-FOCUS or control the lens setting, the best way to learn is to do a lot of testing.  I am still learning myself and learn even more by testing.  It's best to know your equipment very well, so it all becomes secondary.

The chart below gives you a visual example with the various lens number settings.  Usually lenses that open up to f/2.8 are far more expensive than ones that are in the 3.5-4.5 range.

If you have any questions, please don't hesitate to ask in the comments section.