Depth of Field is the concept where when you take a picture with your camera, objects that are further back are less focused than items that are closer. This effect is quite easy to exaggerate with an SLR camera because you can adjust the Aperture (the amount the lens opens when a picture is taken). On a good lens, you can adjust the aperture down to as low as 1.4 or 1.8.
The image above demonstrates a very shallow (or narrow) depth of field. Note how the fence is very focused while everything behind it is very very soft.
Depth of field is often taken for granted by those of us who use SLR cameras. It’s quite easy for us to achieve. If, however, you use a point and shoot camera (think small pocket cameras), there’s almost no depth of field. All pictures are taken at a very small aperture (small F stop) meaning everything in the foreground and background appears to be in focus, which is the opposite of what you see above.
Now that we’ve gotten the technicalities out of the way, and your brain is dribbling out your ears, here’s a very good tutorial for replicating (to some degree) the effect of a wide open lens (a lens with a high aperture) in Adobe Photoshop.
If you would like more information on the use of apertures in photography, check out this site which is as thorough as I’ve ever seen on the topic. And don’t be afraid to delve into topics like this. It helps to know stuff like this, and it will only help you to take better pictures, regardless of your camera.
[tags]photography, how-to, aperture, explanation, reference[/tags]