by Lauren Scott Posted by on N-Photo July 4, 2022
Learn how to get proper focus in every shot, and how changing the aperture changes the look
To explain what depth of field is, it might be helpful to start by looking at the lens help. The lens can only focus precisely at one distance at a time, but things closer or further away than the subject can still appear sharp. This "sharpness zone" may be so shallow that it barely exists, or it may extend to the distant horizon.
"Zone of apparent sharpness" is a good working definition of depth of field (DoF). Only perfect focus at one distance will produce precise sharpness, but things in front and behind it may still appear sharp - with blur at either end too slight to be noticeable. In the real world, this sharpness matters. If something looks sharp, even if in theory it isn't, it's sharp enough for our purposes.
Most landscape photographers will usually try to make everything clear, but this is a matter of choice, not law. In sports or portraiture, a shallow depth of field can be used because it takes distracting backgrounds and foregrounds out of focus.
controls depth of field
Depth of field varies greatly and is controlled by three factors. The first is aperture (opens in new tab) , which means the aperture of the lens. Most people know that a wider aperture produces a shallower depth of field, but remember that aperture numbers are fractions, so f/16 is a narrower option and f/4 is a wider option.
Of course, how you set your camera's aperture depends on the make and model. For example, you can use aperture priority (A on the mode dial) and adjust settings using the command dial (on cameras with two dials, use the sub-command dial on the front of the camera). As the aperture changes, the camera adjusts the shutter speed to keep the overall exposure constant.
The next factor that affects depth of field is the focal length of the lens. Longer focal lengths reduce depth of field, while shorter focal lengths increase depth of field. A wide-angle setting, such as the 18mm end of the kit lens, is good for keeping everything sharp, while blurring the background requires using a longer focal length, such as 55mm+.
The third factor is the distance between the camera and the subject. The smaller this is, the less depth of field you have, but the depth of field extends beyond the focal point and to the front - so focusing on the farthest point won't give you the greatest depth of field.
However, the three factors that control depth of field do not always work in harmony. You may decide to switch to the wide angle lens to improve the depth of field. This makes your subject appear smaller in the frame. To fix this, you need to get closer, but this reduces the depth of field.
Sneak Peek
Looking through a DSLR's viewfinder doesn't show the effect of changing the aperture - it shows the view with the lens wide open, but predicting the end result isn't pure guesswork. Many Nikon DSLR cameras have a depth-of-field preview button that stops the lens down to a selected aperture. Unfortunately, this darkens the image, making it harder to see.
With the electronic viewfinder of the Nikon Z series, not only is the lens always zoomed out to the selected aperture, allowing you to judge depth of field, but the brightness reflects the exposure setting so you can see the image clearly. The same goes for using live view on a DSLR. It's true that some DSLRs (such as the D3500) don't have a depth-of-field preview button, so you'll have to use live view if you want to know how much of your scene is in focus before shooting.
Three ways to affect depth of field: aperture, distance and focal length
The picture below is clear at a glance. Everyone can understand it, so I won’t translate it here.
