In the topic of today's article, we will try to reveal such a concept as DOF. And in this case we are not talking about a common disease, but about the depth of field in the photo. It completely sounds like this - the depth of the sharply depicted space.
Each person whose activities are related to such a sphere knows perfectly well what this definition means. But we, ordinary users, want to understand something. This is especially true for aspiring photographers.
Many of us do not even suspect that each person is faced with a depth of field in a familiar life. But is this possible? The answer lies in our vision. To convince these reasons, it is worth giving a simple example.
First, take a piece of paper and make a small hole in it 2 cm in diameter. Position it at a distance of 20 cm from your eyes and try to make it so that you can simultaneously see the sheet of paper and what is within the hole. Is this possible ?! And if now close it on the other hand with your hand, what then? This simple example explains the depth of field.
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 an individual vision and perception.
As confirmation, you can consider the numerous photos that flooded the Internet. Looking at them, one 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”, the abbreviation “depth of field” is used, which is reflected in numerous Internet sources or specialized magazines.
For any specialist whose activities are related to professional photography, IPIG 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 over the entire surface of the frame or effectively blur the front or background according to the idea or as needed.
The technical side of the issue of depth of field in photography
A simple example with a sheet of paper, which was discussed above, shows that any camera is similarly arranged - an increase in the depth of field leads to a sharper focus. Otherwise, the focal plane will become worse. If you look at a photograph, the immediate environment (be it a person, an object or a small group of objects) will be in focus, and everything else will be blurred. In other words, we concentrate on what is closest to us, and the distant environment is overlooked.
In the device of any camera, the depth of field is directly dependent on several important parameters:
- lens aperture;
- distance to the object;
- focal length.
In simple terms, DOF is the area or area where the subject is visible with maximum clarity and sharpness. But what does this give us?
Explanation of Characteristics
What is the depth of field in photography for beginners? Aperture is calculated by a simple formula: f / "number". And the smaller this “number”, the greater the lens aperture. Accordingly, the depth of field is reduced. The distance to the object or group of objects also matters. The farther they are located, the greater the depth of field will end up. If you take two pictures from different distances, 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 soap camera and take something from a distance of 2-3 centimeters, the result will be a blurred background, since the area of the matrix is quite small.
Now it’s worth touching the focal length - with its increase, the depth of field decreases. In other words, at a wide angle (short focus), the depth of field will be enormous, while at a small angle (long focus) the depth of field will be scanty.
What is characteristic, portrait shooting requires precisely a shallow depth of field. This allows you to distinguish the model from the rest of the environment, which is not worthy of attention. What determines the depth of field in photographs in addition to the factors already listed?
In fact, the aperture is an element of the lens design, which is able to adjust the diameter of the hole that transmits a stream of light onto the film (in old devices) or the matrix (modern devices). In other words, the number of transmitted light waves is adjusted precisely by the diaphragm.
In English, this element bears the name - aperture, however, in the generally accepted marking, the Latin letter F is used to indicate the degree of opening of the diaphragm. With the opening of the hole, the depth of field decreases, exactly the opposite.
The maximum and minimum aperture value largely depends 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 the depth of field in the photo, the aperture can affect the shutter speed. The more light that the lens can transmit, the less time the camera needs to keep the shutter open.
Crop factor of the camera matrix
In that era when photographs were taken using 35 mm film, this concept was not mentioned. 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 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 photographs, respectively, and the quality of images. And that means a choice of camera. Meanwhile, the crop factor is closely related to the 35 mm film, because it is a coefficient indicating the difference between the size of the digital device matrix and the traditional film frame (35 mm). It is calculated by the ratio of the diagonal of a standard frame (43.3 mm) to the diagonal of a frame with an incomplete matrix.
Here, the diagonal of the frame is always mentioned, since the crop factor is based precisely on this parameter. But in order to visually see the differences in size, you need to square the crop factor. For example, the area of the APS-C of the CANON sensor (crop factor of 1.6) will be: 1.6 x 1.6 = 2.56. So many times it is less than the area of a full frame.
And since the whole frame is taken as the basis, accordingly, the coefficient cannot be less than one.
About what is the depth of field in photography, a simple language has already been said. But novice photographers need the right knowledge regarding the crop factor. One may come across an erroneous opinion that this coefficient can increase the focal length of the lens, which does not actually happen. Smaller sensor sizes can reduce the viewing angle of the lens, thereby reducing the field of view of the frame. In other words, in the end, we have nothing but the cut out central part of the full frame.
And given that the electronics automatically scale the image onto the screen and stretch it, the illusion of increasing the focal length is created. In fact, the actual focal length of the lens as it was, remains the same, and it is always indicated in relation to the full frame.
The optimal depth of field is selected depending on the shooting tasks. Many novice photographers make the most common mistake - to take pictures using the recently acquired aperture lens with maximum aperture. Yes, in some cases this is justified, but not always.
How to adjust the depth of field in a photograph? When shooting a portrait with a shallow depth of field, it may turn out that only the eyes will be in the sharpness zone, 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 zone of sharpness. Such a picture looks quite natural.
In this regard, there is no need to always fully open the diaphragm, and in most cases it is better to cover it with a couple of steps. As a result, the depth of field will be optimal, and blurring will be within acceptable limits.
If you want to take a group shot, there is a need for optimal depth of field. For this, the diaphragm should cover itself more strongly - in the range of values from f / 8 to f / 11 with good lighting outdoors.
Hyperfocal Distance (GR)
There is another important term that combines commercial photography and depth of field - hyperfocal distance or GR. 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, it is the same DOF, but with a focus on infinity.
It is important to consider some points:
- With an increase in the degree of aperture opening, GR also increases.
- The wider the angle of the lens, the lower the GR.
In ultra-wide-angle lenses, GR values start from two to three meters, which is pretty close.
As for the focal lengths, much larger distances appear here - from 100 meters or more. For this reason, to create landscapes, preference is mainly given to the values of the closed aperture and wide-angle lenses.