What is depth of field in photography?

2024 Author: Sierra Becker | [email protected]. Last modified: 2024-02-26 03:35

In the topic of today's article, we will try to reveal such a concept as the depth of field. And in this case, we are not talking about a common disease, but about the depth of field in photography. It fully sounds like this - the depth of field of space.

Every person whose activities are related to this area knows perfectly well what this definition means. But we, ordinary users, want to understand something. This is especially true for beginner photographers.

General information

Many of us are not even aware that each person is faced with depth of field in everyday life. But is it possible? The answer lies in our vision. To make these arguments convincing, it is worth giving a simple example.

Let's start with a sheet of paper and make a small hole in it2 cm in diameter. Position it from your eyes at a distance of 20 cm and try to make it so that you can simultaneously see the sheet of paper itself and what is within the hole. Is it possible?! And if now close it on the other side with your hand, what then? This simple example explains depth of field.

Professional term

We have already familiarized ourselves with the depth of field - this is the space in the photograph in which the subject looks as sharp as possible, that is, clearly, and everything else is blurred. At the same time, it should be understood that the depth of field in photography is a rather subjective and conditional concept, since each person has individual vision and perception.

As a confirmation, you can consider the numerous photos that flooded the Internet. Looking at them, you can understand that all people have their own perception of image sharpness.

From a professional point of view, instead of the colloquial term "depth of field", it is the abbreviation DOF that is used, which is reflected in numerous sources on the Internet or specialized magazines.

For any specialist whose activities are related to professional photography, DOF is by no means an abstract concept! These people see much more here - a powerful tool for focusing attention on any particular object. With it, you can display the entire environment in maximum clarity across the entire surface of the frame, or effectively blur the front orbackground according to the idea or as needed.

The technical side of depth of field in photography

The simple sheet of paper example discussed above shows that any camera works in a similar way - increasing the depth of field leads to sharper focus. Otherwise, the focal plane will become worse. If you look at any photo, then the immediate environment (whether it be a person, an object or a small group of objects) will be in focus, and everything else will be blurred. In other words, we focus on what is closest to us, and the far environment is overlooked.

In the device of any camera, the depth of field is directly dependent on several important parameters:

• lens aperture;
• distance to object;
• focal length.

In simple terms, the depth of field is that section or area where the object being filmed is visible with maximum clarity and sharpness. But what does this give us?

Specifications explained

What is depth of field in photography for beginners? Aperture is calculated using a simple formula: f / "number". And the smaller this “number”, the greater the lens aperture. Accordingly, the depth of field is reduced. At the same time, the distance to an object or group of objects also matters. The farther they are located, the greater the depth of field in the end. If you take two pictures from differentdistances, for example, let it be 5 meters and 50 cm - the depth of field in the photographs will be very different.

In other words, if you set the macro mode on the camera-soap box and take a picture from a distance of 2-3 centimeters, you will end up with a blurry background, since the area of \u200b\u200bthe sensor here is quite small.

Now it's worth touching on the focal length - as it increases, the depth of field decreases. In other words, at a wide angle (short focus) the depth of field will be simply huge, while at a small angle (long focus) the depth of field will be meager.

Typically, for portrait photography, it is precisely a shallow depth of field that is needed. This allows you to distinguish the model from the rest of the environment, which does not deserve attention. What determines the depth of field in photographs, in addition to the factors already listed?

Aperture value

In fact, the diaphragm is a lens design element that is able to adjust the diameter of the hole that transmits light to the film (in old devices) or the matrix (modern devices). In other words, the number of passing light waves is adjusted precisely by the diaphragm.

In English, this element is called aperture, however, in the generally accepted marking, the Latin letter F is used to indicate the degree of opening of the aperture. With the opening of the hole, the depth of field decreases, and vice versa.

The maximum and minimum aperture value is largelydepends on the design features of a particular lens. Often, many cameras come with a lens with a minimum aperture value of f/3.5.

In addition to depth of field in photography, aperture can affect shutter speed. The more light the lens can let in, the less time the camera needs to keep the shutter open.

Crop factor of the camera matrix

In the era when photographs were taken using 35mm film, this concept did not exist. The standard was uniform and therefore there was no confusion. But with the development of progress, many manufacturers have new opportunities for the manufacture of electronic photosensitive sensors, and of almost any size. Thus began the era of digital photography.

Now the crop factor is the main indicator that affects the depth of field in photos, respectively, and the quality of the pictures. And that means choosing a camera. Meanwhile crop factor (crop factor) is closely related to 35-mm film, because it is a factor that indicates the difference between the size of the matrix of a digital device and a traditional film frame (35 mm). Calculated by ratio of the diagonal of a standard frame (43.3 mm) to the diagonal of a frame with an incomplete matrix.

The diagonal of the frame is always mentioned here, since the crop factor is based on this parameter. But in order to visually see the differences in size, you needcrop factor squared. For example, the area of the CANON APS-C sensor (its crop factor is 1.6) will be equal to: 1.6 x 1.6=2.56. It is so much less than the area of the full frame.

And since the full frame is taken as the basis, accordingly, the coefficient cannot be less than one.

Common False Assumption

What is depth of field in photography has already been said in simple terms. But beginner photographers need the right knowledge of crop factor. You may come across an erroneous opinion that this coefficient is able to increase the focal length of the lens, which in reality does not happen. Smaller sensor sizes can reduce the angle of view of the lens, thereby reducing the field of view of the frame. In other words, in the end we have nothing more than a cut out central part of the full frame.

And taking into account the fact that the electronics automatically scales the image onto the screen and stretches it, an illusion of increasing the focal length is created. In fact, the actual focal length of the lens is what it was, and remains so, and it is always indicated in relation to the full frame.

Scope of application

The optimal depth of field is selected depending on the shooting tasks. Many novice photographers make the most common mistake - to take pictures with a recently acquired fast lens with a maximum aperture. Yes, in some cases it is justified, but not always.

Howadjust depth of field in photo? When shooting a portrait with a shallow depth of field, it may turn out that only the eyes will be in the field of focus, while the tip of the nose will be blurred. Whether it will turn out beautifully as a result is a moot point. But if a person's head is slightly turned to the side, then the near eye will be clear, but the distant eye will be outside the sharpness zone. This shot looks quite natural.

Because of this, it is not necessary to always fully open the aperture, and in most cases it is better to cover it a couple of stops. As a result, the depth of field will be optimal, and the blur will be within acceptable limits.

If you want to take a group shot, you need an optimal depth of field. To do this, the aperture must be covered more - in the range from f / 8 to f / 11 in good outdoor lighting.

Hyperfocal distance (HR)

There is another important term that brings together commercial photography and depth of field - hyperfocal distance or HF. This definition should be understood as the distance from which, regardless of the degree of aperture opening, all objects and objects will be with maximum sharpness. That is, this is the same depth of field, but with focus on infinity.

It is important to take into account some points:

• As the degree of aperture increases, so does the GR.
• The wider the angle of the lens, the smaller the GR.

Ultra wide-angle lenses start at 2-3 meters, which is pretty close.

As far as long-range lenses are concerned, much longer distances appear here - from 100 meters or more. For this reason, shutter speeds and wide-angle lenses are preferred for landscapes.