The photo at left is a composite of two photos that were taken only moments apart. As you can see, there is a noticeable difference in the background between the two. An experienced photographer would identify the bottom half of the composite as having a long depth of field because both the chess piece in the front and the chess piece in the back are in sharp focus.

If this concept of "depth of field" isn't immediately clear to you, it may be easier to think in terms of "depth of focus": every element from front to back in the bottom half is in focus, thereby having a long depth of focus.

On the other hand, the top half would be described as having a short depth of field (or depth of focus) because while the front piece is in sharp focus, the back piece is blurry, or soft.

Unless you have studied photography, you may not know how to control your depth of field. Once you have read this lesson, however, you will know how to adjust the settings in your digital camera to create the look you want every time.

As we've seen above, depth of field can vary greatly from photo to photo. Technically, the depth of field is determined by the amount of subject matter that stays in focus both in front of, and behind, the point of focus. So before you make changes to your depth of field, you first need to set the focus mode of your camera.

Controlling Your Focus Manually
In most mid-range digital cameras, there are at least two focus modes available: Auto amd Manual. While Auto-focusing allows you to lock down your focus quickly, Manual focusing enables you to be precise with your point of focus. This is particularly useful when shooting small stationary objects up close. Here, we demonstrate how to set Manual focus in your digital camera.

NOTE: We used a mid-ranged compact digital camera for this lesson, and most of the techniques demonstrated here can be achieved with whichever mid-to-upper range digital camera you happen to own. Simply refer to your owner's manual while reviewing the general techniques illustrated in this lesson.

Once the camera is powered up, locate the Focus mode menu (either on the back of the camera or in the internal menu) and use the controls to select MF [Manual Focus] (figures 1 & 2).

The most important thing to remember is that your aperture setting controls your depth of field. The smaller your aperture number, or "f/stop", the shorter your depth of field will be. On the LCD of your camera, you should see a number grouped with the letter F. This is your aperture setting, or "F/stop". Refer to your particular camera manual to see how to adjust your aperture setting (figures 4 & 5).

There should also be another number visible on the LCD, but without the F. This number represents your shutter speed setting, which determines how long the shutter stays open after you push the shutter button. Once your aperture is set, the shutter speed can be adjusted to accommodate the proper exposure.

One of the nice things about digital cameras is that if you take a shot and it's either too light or too dark, you can immediately make adjustments to the shutter speed until you render the proper exposure. Likewise, if you want to maintain a certain shutter speed, you can make adjustments to the aperture to render the proper exposure.

To demonstrate different depths of field, we took some shots of chess pieces at different aperture settings. We placed three pieces on a white table next to a 12-inch ruler, each piece six inches apart. After manually focusing on the middle piece, we took shots at two different aperture settings: one at f/8 (Figure 7) and one at f/2.8 (Figure 8).

Notice in the top half of the image how the chess pieces in the foreground and background are slightly out of focus or "soft". This is because the focus area, or depth of field, is limited to the area around the center chess piece.

Now notice in the bottom half of the image how the chess pieces in the foreground and background are just as focused as the center piece. This is because our depth of field (f/8) is deep, allowing everything to stay in focus from front to back. Remember, the higher the aperture number, the deeper the depth of field.

Notice how quickly the focus drops off in the top half (f/2.8), whereas the falloff is barely perceptible in the lower half (f/8). The advantage to long depth of field is that every element in the shot is clearly identifiable because it is in focus. The advantage to a limited depth of field is that the viewer's attention is drawn to specific elements that are in focus.

Now that you know how to control your focus and depth of field, let's examine the Macro focusing functionality of this and other mid-range digital cameras. Shooting in a Macro mode magnifies the effects of depth of field and works beautifully to increase the size of small items, such as jewelry, flowers and these chess pieces.

At the f/2.8 setting, only the rear piece stays in focus. And because of its distance from the lens, the rear piece is rendered as large as can be while still maintaining focus. At the f/8 setting, however, both pieces are in focus because of the longer depth of field, yet this is about as large as we can render the front piece without it going soft.

As with many mid-ranged digital cameras, this camera has a Macro function that allows you to bring the camera in very tight on your subject. We set the focusing mode to Macro and were able to place the front piece about 3 inches closer to the camera while still maintaining sharp focus.

Look at the back piece now. At 2 inches back from the first piece, it's almost unrecognizable at f/2.8, and there is even a noticeable difference at f/8.

Note that some cameras even have a Super Macro setting that allows you to bring the lens to within 1 inch from your subject! By experimenting with focal distances and aperture settings, you will be able to achieve the look you're after in most any situation.

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