Aperture-priority AE This is the mode to choose when your primary emphasis is with Depth-of-Field ó that is, how much of the scene from front to back is sharply in focus. With Aperture-priority AE, you select the aperture, and the camera chooses an appropriate shutter speed. Opening up the aperture reduces the zone of in-focus elements. Closing down the aperture increases depth-of-field. In general, with the lens set at its widest aperture ó f/1.4, for example, then only the subject you have focused on will be sharp and everything in front and behind the subject will be blurred. On the other hand, with the aperture closed down all the way to f/22, then almost everything from a few feet away to infinity will be sharply in focus. Remember, closing the aperture down means less light comes in so you need a slower shutter speed. Also, when the focus point is at infinity, regardless of whether then lens used is a wide-angle, standard or telephoto, everything else in focus range of infinity be in sharp focus. If you want lots of depth-of-field, you may end up with a shutter speed that's too slow for hand-held photography. In this case, use a tripod or switch to a faster film. Or you own any one of the four Canon Image Stabilizer (IS) EF USM lenses currently available, just use the lens in its IS mode to compensate for any camera shake that might result from using a slower shutter speed. Keep in mind that maximum depth-of-field is not always the goal. Sometimes you may want to blur non-essential elements. Portraits or action sports shots often look best when the background is out of focus, since this centers attention on the main subject. For any kind of picture where you want to isolate the main subject, you can shoot with the lens wide-open, enjoying the fastest possible shutter speed and relying on the AF system of your EOS camera to make sure you're in focus. << Back to Main . 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . 11 .