​The importance of depth of field in shooting

Depth of field is the area of clarity that is acceptable before and after a clearly focused focus. When the depth of field is shallow, canvas prints the focus is a very thin plane that falls on the object, parallel to the plane of the sensor in a digital camera. When conditions affecting the depth of field change, such as when the lens aperture Narrows, this apparent clarity extends in front and behind the focal plane of the lens. By controlling the depth of field, the photographer can control the sharpness of the subject and the background.

In the basic method of picture composition, print canvas online it is very common to deal with background by using depth of field. The effect of shallow depth of field can be achieved by using a long focal length or a large aperture or by shortening the shooting distance. Shallow dof can blur complex backgrounds and highlight subjects. The picture above on the right is a schematic of the most basic shooting method. The flowers closest to the camera represent the foreground, followed by the medium and background. The right picture below is the shooting method that highlights the effect of depth of field through the process of blur processing. The foreground and background are both blurred to highlight the subject of the middle shot.

The above image shows a cute cat sitting on its stomach. The photographer used shallow depth of field, the main body is prominent, panoramic canvas print creating a beautiful background and soft picture effect.

Ii. Factors affecting the depth of field

How much depth of field a photo should have depends on the information the photographer is trying to convey. The above picture on the left shows the close-up of the pet dog, shot with f/3.2. The depth of the scene is focused on the eyes of the pet dog, and the dog's eyes are perfectly displayed.

In photographic creation, the three main factors affecting the depth of field are as follows. We can adjust these factors to change the effect of depth of field.

1. Shoot the size of the time circle

The focal length of the lens

The distance between the camera and the subject

The specific relationship between depth of field and the above three elements is as follows.

Aperture size: the larger the aperture, the smaller the aperture value, the shallower the depth of field; the smaller the aperture, the larger the aperture and the deeper the depth of field.

Focal length: the longer the focal length, the shallower the depth of field; the shorter the focal length, the deeper the depth of field.

Shooting distance: the closer the camera is to the subject, the shallower the depth of field; the farther the camera is from the subject, the deeper the depth of field is.

Depth of field, foreground and background

1. Focus on the foreground

We all know that when we view a scene, the scene in the viewfinder is divided into the foreground and the background. The foreground is the part closest to the camera. Focusing on the foreground will highlight the foreground as the subject of the picture. In general, when the background of the picture is very messy, the foreground can be focused to make the background blurred, so as to weaken the adverse effect of the background.

2. Focus on the backshot

Backshot is the person or thing behind or near the back of the subject in a shot. The background, corresponding to the foreground, is sometimes the subject or companion of the scene.

Focusing on the backview will show the backview as the subject of the subject, and the parts outside the backview will be blurred. This kind of contrast between reality and fiction often leaves a very deep impression on people.

Normal photography generally requires a clear focus so that the subject can be clearly presented. However, sometimes, it is one of the techniques of photographic expression to make the focus of some scenes blurred purposefully in the picture. For example, in the picture, by selectively placing the foreground branches and leaves outside the focus, the photographer intentionally goes beyond the foreground and focuses only on the reflection of the trees in the rear water surface, thus making the branches and leaves become the background foreground, and the contrast between the real and the virtual gives a deep impression.

3. Control method of depth of field

Different apertures create different depth of field effects when photographing flowers in flowers. It can be seen from the picture that the depth of field changes with the aperture.

4. The method of obtaining the maximum and minimum depth of field

Depth of field control is one of the basic techniques of photography. We can also reduce the depth of field to just clearly show the main object and let the secondary objects fade away. The effect of depth of field on photo composition is very obvious.

How do you get the deepest depth of field? We can obtain the deepest depth of field by the following three measures:

try to use a wide Angle or short focal length lens

when shooting, try to lengthen the shooting distance

minimize aperture

Sometimes, the photographer wants the picture to be something more than it really is, such as blurring the environment to make the subject clear. This requires the use of shallow depth of field technology, or "selective focus." How to get the minimum depth of field? There are also three measures:

try to use the maximum focal length of the lens or shoot with a telephoto lens

try to get closer to the subject

use maximum aperture

5. Control the depth of field through aperture

Although these three elements can all control the depth of field effect, the most maneuverable element in photographic creation is to adjust the aperture. Since changing the focal length or shooting distance will change the overall composition and perspective relationship of a photo, if the composition and perspective relationship of a photo have been determined, the depth of field can only be controlled by changing the aperture. The following two pictures are taken at the same focal length, and the difference in depth of field is realized by adjusting the lens aperture: the larger the aperture, the shallower the depth of field; the smaller the aperture, the deeper the depth of field.

4. Control the degree of blur by adjusting the background

Among the three factors that affect depth of field, shooting distance (the distance between the lens and the subject) plays an important role. There are two ways to change the shooting distance: one is to move the camera to change the distance between the camera and the subject; the other is to change the distance between the subject and the background. Other factors remain the same when the distance between the subject and the background is changed. At this time, the depth of field of the picture will not change, but because the background is farther away from the clear depth of field, the background in the photo will be more blurred. That is to say, by changing the shooting distance, the degree of virtual image can be controlled.

In the above two photos, the first one was taken by the photographer from the top. The flowers are close to the ground, and the ground is dim, and the degree of hollowing is not particularly obvious. When the photographer takes the second picture horizontally from the side, the background in the picture is far and wide and the distance from the subject is far, so the effect of blurring the background is more obvious.

Control the depth of field by adjusting the focal length

We can also control the depth of field by adjusting the focal length of the lens. The shorter the focal length, the deeper the depth of field; the longer the focal length, the shallower the depth of field.

However, in the actual shooting, the adjustment of the focal length is often subject to a lot of restrictions, because the change of focal length will change the view Angle and frame range of the picture at the same time, and the view Angle is often the most important factor to determine the composition of a photo, so changing the focal length is often not the first choice for the photographer to control the depth of field.

When is it possible to control the depth of field by adjusting the focal length? This method can be used to control the depth of field if the subject is relatively simple, the shooting point can move back and forth, and there is no obvious perspective relationship in the picture.

In the picture, wide-angle lens is used to shoot close to the sculpture. The background is not blurred enough, and the elements in the background can still be seen. At this point, the photographer steps back and shoot with a telephoto lens, which immediately shallows the depth of field. On the left, when shooting a large indoor scene with a wide-angle lens, the focal length cannot be simply adjusted to control the depth of field.

The correct understanding of the degree of virtual

Depth of field and accurate focus are important for clarity. Some beginners might think that a part of a photograph is either clear or blurry. In fact, this kind of understanding is too absolute, the degree of blur outside the focus of the image is also different, can show a linear change, that is, from slightly fuzzy to completely fuzzy. From the inside of the focal point to the outside of the focal point, there is a trend of gradual change from clear to gradually blurred, that is, the degree of blur.

The subjects in the photo are really clear only when they are in the focal plane. All the points that are not in the focal plane are more or less blurred in the photo, but the weak blurring effect cannot be distinguished by the naked eye. In fact, in many photos, because the depth of field is not shallow enough, the objects that are not in focus can still be clearly identified, which weakens the attention of the viewer to the subject. In this case, the depth of field needs to be shallower.

On the contrary, if the environmental information of the picture, such as the picture on the left, needs to be explained, then the depth of field can be controlled a little deeper, and the picture changes gradually from clear to fuzzy, cheap large canvas but some background elements are still clearly discernible, the audience can understand the relevant information of the scene. As a background element, even if the area outside the focal point is not very clear, it can also let people know the background and other information of the photo taken.