Basic Photo Tip: Angle of view and depth

Almost everyone who owns a camera has a zoom lens, whether it is on a point-and-shoot camera or they have one for their SLR. But what exactly happens when you zoom in or zoom out with your lens? Why does your subject get closer or further away? Angle of view is the term for how the camera shows a wider or narrower angle.

It is a difficult subject to understand. Personally, I don't completely understand it myself. But I do know that if I zoom in on a subject the angle of view narrows significantly, while if I zoom out the angle of view widens.

There are three web pages that I would recommend to see the differences in angle of view and get a better understanding. The first is the Wikipedia entry on Angle of View, particularly the section on lens types and effects.

The second is a cool page that lets you click on the various types of lenses from Canon and see the differences in angle of view. You can also click on the different Canon SLR cameras and see how the camera's digital sensor size affects the view.

The third is from Canon itself and it is a little program that lets see all of this simulated in one picture. It starts from a 15mm fisheye to a 1200mm super-telephoto lens.

There's one more important factor to consider when using lenses. Zooming in on a subject also narrows the depth of field, while zooming out increases it. Depth of field refers to the portion of the photo that is in focus. The other factor that affects depth of field is what aperture you have your lens set to.

Although this is on a small scale in a closeup photo, here is a good example of depth of field.