Your Nikon D5500 allows you to manipulate depth of field. Getting familiar with the concept of depth of field is one of the biggest steps you can take to becoming a better photographer. Here’s are some things to remember about depth of field:
Depth of field refers to the distance over which objects in a photograph appear acceptably sharp.
With a shallow, or small, depth of field, distant objects appear more softly focused than the main subject (assuming that you set focus on the main subject, of course).
With a large depth of field, the zone of sharp focus extends to include objects at a distance from your subject.
Which arrangement works best depends on your creative vision and your subject. In portraits, for example, a classic technique is to use a short depth of field, as you can see on the left photo. This approach increases emphasis on the subject while diminishing the impact of the background. But for the photo on the right, the foreground figures in St. Peter’s Square were emphasized, so a large depth of field was used, which kept the background buildings sharply focused and gave them equal weight in the scene.
Depth of field depends on the aperture setting, lens focal length, and distance from the subject, as follows:
Aperture setting (f‐stop): The aperture is one of three main exposure settings. Depth of field increases as you stop down the aperture (by choosing a higher f‐stop number). For shallow depth of field, open the aperture (by choosing a lower f‐stop number). In the f/22 version on the left, focus is sharp all the way through the frame; in the f/2.8 version on the right, focus softens as the distance from the flag increases. Both images were taken using the same focal length and camera‐to‐subject distance, setting focus on the flag.A lower f‐stop number (wider aperture) decreases depth of field.
Lens focal length: In lay terms, focal length determines what the lens “sees.” As you increase focal length, measured in millimeters, the angle of view narrows, objects appear larger in the frame, and — the important point for this discussion — depth of field decreases. Additionally, the spatial relationship of objects changes as you adjust focal length.
As an example, the picture below compares the same scene shot at a focal length of 127 mm and 183 mm. The same aperture and camera‐to‐subject distance was used for each shot, setting focus on the parrot.Zooming to a longer focal length also reduces depth of field.
Whether you have any focal length flexibility depends on your lens: If you have a zoom lens, you can adjust the focal length by zooming in or out. If you have a prime lens — that is, not a zoom lens — the focal length is fixed, so scratch this means of manipulating depth of field.
Camera‐to‐subject distance: As you move the lens closer to your subject, depth of field decreases. This statement assumes that you don’t zoom in or out to reframe the picture, thereby changing the focal length. If you do, depth of field is affected by both the camera position and focal length.
Together, these three factors determine the maximum and minimum depth of field that you can achieve, as follows:
To produce the shallowest depth of field: Open the aperture as wide as possible (the lowest f‐stop number), zoom in to the maximum focal length of your lens, and get as close as possible to your subject.
To produce maximum depth of field: Stop down the aperture to the highest possible f‐stop number, zoom out to the shortest focal length (widest angle) your lens offers, and move farther from your subject.
A few final tips related to depth of field:
Aperture‐priority autoexposure mode (A) enables you to easily control depth of field while enjoying exposure assistance from the camera. In this mode, you rotate the Command dial to set the f‐stop, and the camera selects the appropriate shutter speed to produce a good exposure. The range of available aperture settings depends on your lens.
For greater background blurring, move the subject farther from the background. The extent to which background focus shifts as you adjust depth of field also is affected by the distance between the subject and the background.
In Live View mode, depth of field doesn’t change in the preview as you change the f‐stop setting. The camera can’t display the effect of aperture on depth of field properly because the aperture doesn’t actually open or close until you take the photo. However, you can gauge the depth of field produced by the focal length and subject‐to‐camera distance in the preview.