Tip 5: Hyperfocal Distance Every aperture has a corresponding hyperfocal distance, or the distance at which to focus to obtain optimum depth of field. Focusing at the hyperfocal distance maximizes the depth of field for that aperture: the depth of field extends from half the hyperfocal distance out to infinity. In the Rocky Mountain dawn picture, the nearest boulders were about 20 feet away. This meant I needed a hyperfocal distance of 40 feet, which I could accomplish using f/2 with my 24mm lens (although I shot at f/4 for an extra safety margin). Tip 6: Depth Of Field Preview With an SLR camera the viewfinder sees the world through the lens—but always at its widest aperture (and narrowest depth of field), regardless of what f/stop is selected. Some SLRs have a depth of field preview button that enables you to stop down the lens to the shooting aperture so you can see what the final picture will look like. I used this feature when taking the photo of the holly in snow to verify that the background would be sufficiently out of focus. This preview feature also enables you to discover if some distracting foreground element, blurred to the point of invisibility at the widest aperture, makes an unfortunate appearance when the lens is stopped down. Tip 7: Keep the Camera Parallel When depth of field is limited, try to arrange the dominant plane of your subject to be parallel to the camera back. This keeps the subject fully within the narrow zone of crisp focus. Depth of field is especially small with close-up photography, so in the caterpillar image I took pains to line the camera up exactly broadside to the body of the creature. Tip 8: Change the Focal Length The focal length of the lens you use is typically determined by your choice of composition. For those occasions that lend you the freedom to alter the focal length, however, longer focal lengths have inherently less depth of field than shorter lenses. Thus, you can zoom or change lenses to alter the depth of field. I shot the pair of horses with a 200mm lens, and there was no way I could keep both in focus with the limited depth of field of this telephoto lens. Tip 9: Blur the Foreground Choosing a wide aperture and focusing on a distant object will throw foreground objects out of focus. Often this makes the foreground objects distracting if they are only slightly out of focus, but it can sometimes blur them to invisibility as a means of reducing clutter in an image. Even if nearby objects are not totally invisible, "shooting through" the foreground can add atmosphere to a photograph. By shooting through some strongly-colored foreground leaves using a wide aperture in the fall foliage image, I meant to convey a soft romantic feel. Quick Fixes Move The Camera Moving the camera closer to the subject decreases depth of field (for a given aperture and focal length), while moving away will increase it. Don't attempt to move away to increase depth of field and then switch to a longer lens to refill the frame with the subject. You'll wind up with same depth of field you started with. The laws of optics dictate that for a given subject size in the photo, distance and focal length cancel out and only the aperture determines the depth of field. Move The Subject If you are at liberty to move your subject, moving it away from the background will improve a selective focus image, since the background is then farther from the zone of sharpness. On the other hand, if you want the background sharp, move the subject closer to the background. When It Just Doesn’t Matter In situations in which the depth of field just doesn't matter, like when you are shooting something at infinity on the horizon or a flat subject viewed head on, shoot with the lens stopped down a couple or so stops from wide open. For most lenses this is the "sweet spot" where they are at their very sharpest.