Depth of Field Experimentation in Digital Photography
Controlling the depth of field (near-to-far sharpness) in a photo allows you to dramatically change the look of your digital images. Going for a lot of depth of field gives you a photo in which everything looks sharp from right in front of the camera to the distant horizon. When you want the subject to look sharp but you want everything in front of and behind the subject to look soft and blurry, opt for very little depth of field.
Three variables determine the depth of field in your digital exposures: aperture, focal length, and focused distance (the distance to your focused subject). Adjusting any one of these variables without adjusting the other two changes the depth of field. If you play with two or more of these variables, the depth of field may change even more dramatically; then again, it may not change at all.
To get the most out of depth of field requires a little experimenting. Start with these suggestions, but don’t hesitate to play around with your settings:
To minimize depth of field, use wide apertures and longer focal lengths and move in closer to your subjects. Also, try to avoid having distracting objects right behind your subject. A blurry tree or fencepost growing out of the subject is the kind of thing photographers tend to miss while they’re totally focused on their subject but kick themselves for when they look at the photos later.
If there’s a lot of distance between your subject and the background, the subject will pop out more against the blurry background.
To maximize depth of field, use smaller apertures and wide-angle lenses and back up a bit from your subject. How far back you need to get depends on the lens you’re using and the aperture you choose. Inexperienced photographers are prone to have boring foregrounds in their wide-angle, maximum-depth-of-field photos. To avoid this problem, have a center of interest close to the camera, even if it isn’t your main subject. It could be flowers, a cactus, a spot between the rails of a railroad track, or a yellow stripe in the highway. Whatever it is, put the camera down low and get in close. The center of interest will draw the viewer’s eye into the rest of the frame.
When you just need a medium amount of depth of field, stick with midrange apertures like f/5.6 or f/8 for wide-angle to normal focal length lenses. At longer focal lengths, switch to an aperture of f/11 or f/16.