Depth of field

Depth of field refers to how much of your image will be in sharp focus. Shallow depth is characterized by blurred backgrounds, which is cool for portraits. A deep focus on the other hand has everything tack sharp. The most obvious way to control DOF is by shooting in aperture priority mode. The smaller the f-number, the larger the lens opening and the more shallow your depth of field will be. On the other hand, setting the aperture to a higher f-number, the smaller the aperture (lens opening) which will give you a much greater depth of field or focus.


Another way to control DOF is by subject to camera distance. The closer you move towards the subject, the shallower the DOF becomes. It's a good idea to play with this concept using your digital camera. The results are instant, so it's a great learning experience.

Finally, the focal length of your lens also plays a role in controlling DOF. A wide angle lens, by nature of its design will have a wide DOF. It's almost impossible to blur the background when using a lens with say 20mm or less. On the other hand, a telephoto lens makes for a very shallow DOF.

The best way to become familiar with this concept is to go out and do some experimental photography using various f-stops and camera to subject distances.

If you want to get really technical then you might find this Depth of Field Calculator of value.
I know I made this short and to the point, so if any reader wishes to expand on this subject, please feel free to do so.
Again, the best way to get an handle on DOF is to go out and take a lot of pictures, keep notes and then study your results.

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