Why is aperture important in a camera? This is a strange f-number.

It is important to understand how cameras generally convert incoming light into an image. In order to better understand the principles of the camera, it is better to give a visual.

Imagine a completely dark room that has a window with black panes through which no light enters. If you open it a little, leaving a small gap, you will see a thin strip of light on the opposite wall. If you open the window completely, then the whole room will be filled with light. In both cases, the window was open, but the lighting was completely different. In the camera, the role of the window is performed by the diaphragm, and the role of the wall on which the light falls is the matrix that captures the image. How wide the aperture is opened determines many of the characteristics of future photography. Many, but not all, as the diaphragm is not the only element involved.

What does a diaphragm look like? This is a shutter assembled from the so-called "petals", which, rotating around the circumference, form holes of different diameters (see attached photo). Remember the window analogy? The size of the round hole, which is formed by the movable petals, is similar to the opening of a window. The aperture may consist of a different number of petals, and this also plays a role in the construction of the image.

How to use aperture

In camera settings and on lens markings, aperture characteristics are indicated by the letter f with numerical values ​​assigned to it, for example: f / 1.2 or f / 16. It is important to remember that an inverse relationship is used here, that is, the lower the number, the larger the aperture opening (the wider the “window” is open). Thus, a value of f/1.2 means that the aperture is wide open and there is a lot of light on the matrix, while f/16 means little. When choosing a lens, it is important to pay attention to the f / marking. The lower its value (based on the standard f / 3.5), the better.

At the maximum aperture, a large amount of light enters the matrix. This allows low-light shots without the use of flash and slow shutter speeds. By the way, this is the time interval that determines the time during which the camera shutter remains open, passing light onto the matrix. Going back to the window analogy, this is the amount of time you keep it open.

In addition, the aperture width determines the depth of field. Simply put, this is the number of objects in the frame that are in focus and have clear, sharp edges. With a wide open aperture, their number will be small. Surely many have seen portraits in which a person is captured clearly, and the background is blurred. Or only a small detail of the subject is in focus, and everything around remains blurry. In photography, this beautiful effect is called "bokeh effect".

With the apertures as wide as possible, you can achieve focus on the smallest details, and all other light sources will blur into multi-colored round dots in the picture. Now it's time to return to the aperture blades. The more of them (in standard, inexpensive lenses, there are usually five to seven), the more round the hole they form, and the softer the blur will be.

Unlike wide open apertures, a covered aperture provides greater depth of field, meaning more objects will be in focus. This is widely used when shooting when all the details are needed, such as architectural or landscape.

Also, such aperture settings should be used when shooting with a tripod and slow shutter speeds. Not in low light, but at night, when the number of light sources is minimal. A narrow aperture aperture allows you to take clear pictures without "overexposure", in which all the details are visible.

Knowing the theory, it is important to experiment with different aperture values ​​yourself. By seeing the difference in the shots, you can learn how to choose the right value for different conditions and always achieve excellent results.

This article about what a camera aperture is, first of all, is devoted to beginners in photography, but it will also be useful for skilled photographers.

What is a diaphragm?

In order to , you need to clearly know the main provisions in photography, namely: , aperture (), . This photo article is completely devoted to one of the most important parameters of photography - aperture.

This is the size (diameter) of the aperture through which the characteristics and quality of a still image can be affected in a camera lens.

Hole The , in question, is changed by the petals inside the lens (see figure below).

The most difficult point for beginner amateur photographers who want to know how to learn how to take professional photographs is that the values ​​​​in which apertures are measured are the reciprocal of the relative aperture of the lens. That is, in order to increase the amount of passing light flux, it is necessary to increase this hole (diameter), which means you need to “slightly open” the aperture, namely, set a smaller numerical value of the aperture.

Let's summarize: the larger the aperture number, the less light will pass through the lens. The smaller this number, the more light the lens will let through. That is, the opposite is true. A large aperture is indicated by a smaller number. A smaller aperture (smaller light hole) - a larger aperture number.

What happens to the numbers in reality. To halve the luminous flux, you need to halve the aperture of the diaphragm, while the diameter changes to (the root of two - remember the geometry) 1.41 times. The f-stops used are related precisely to the diameter of the hole in the lens (created by the petals), so a series of numbers comes out, each of which is 1.4 times larger than the previous one:

f/1.4; f/2; f/2.8; f/4; f/5.6 etc.

Thus, for example, changing the aperture from f / 2 to f / 2.8 attenuates the flow of light by half.

What is the aperture of a camera for?

This is a characteristic that affects two image properties at once: aperture ratio (the amount of light passing inside the camera) and depth of field (the distance from the camera between the near and far borders, the objects in which are in focus, that is, clearly visible and not blurry).

Physical aperture of the camera is a description of the diameter of the open hole inside the lens. We mentioned above that the aperture of a camera is thin metal petals that are located in a circle along the rim of the lens. At the time of shooting, they can block the flow of light, connecting and forming a small diameter.

The better the lens, the more such petals, and in the image you can distinguish smooth edges and angular edges of blurry points of light:

The quality of the blur is just the quality of the lens. To show, how camera aperture works, I will give an example of a series of photographs:

Left: closed aperture. In sharpness, almost the entire frame: from the edge of the cup to the table.

Right: open aperture. In sharpness, only the contents of the glass, and everything that moves away smoothly leaves the zone of depth of field.

How does the amount of light depend on the aperture of the camera?

The more open the petals of the camera lens, the more light passes to the photosensitive element (or film). During daylight hours, you can easily adjust and control the aperture of the camera without worrying about the same amount of light.

But! When the overall illumination of the subject being shot is low, your photo may come out dark if you close the camera's aperture. You will say that you can increase (sensitivity). Right. But the sensitivity is, which can interfere with your processing and printing photos. You will answer: we increase. Also true if you stock up on a tripod so that at shutter speeds above 1/125 your shot will contain some sharp detail.

Aperture (aperture) - the relative opening of the lens, which allows you to adjust the flow of light entering the matrix of a digital camera and control the depth of the field of view.

2. Aperture blades

The diaphragm is made up of thin metal blades that cover or open the light opening. There may be more or less depending on the lens model. The number of petals determines the shape of the diaphragm opening - it can be close to a circle, or have the shape of a hexagon. The more petals, the rounder the hole, and the more beautiful the pattern on the lens. For example, when shooting on a lens with a large number of petals, even round spots are formed in the out-of-focus zone, rather than geometric shapes resembling nuts. Modern lenses have rounded petals, despite their small number, provide soft and beautiful background blur.

3. F-number, steps, aperture values

Aperture number is the ratio of the focal length of the lens to the diameter of the aperture, denoted as f / x, where x is its numerical value. The diaphragm controls the flow of light entering the photosensitive elements of the matrix. The larger the f-number, the smaller the aperture, and vice versa, the smaller the f-number, the larger the aperture, respectively, more light passes through. For clarity: f / 16 - closed aperture, f / 1.4 - open.

Aperture values ​​are measured in stops.

1.0

1.4

2

2.8

4

5.6

8

11

16

22

Each stage differs from the previous one by 1.4 times, while the amount of light entering the camera matrix changes twice. For more accurate exposure in modern cameras, there are intermediate aperture values ​​\u200b\u200bthat are equal to 1/3 stops:

1.0	1.1	1.2	1.4	1.6	1.8	2	2.2	2.5	2.8	3.2	3.5	4	4.5	5
5.6	6.3	7.1	8	9	10	11	13	14	16	18	20	22	25	29	32

4. Depth of field

Depth of field (DOF) is the area in which the subject will be depicted sharply, and everything that goes beyond it is blurry.

The depth of field depends on the following parameters:

• diaphragm- the smaller the aperture value (open aperture), the smaller the depth of field; at a closed aperture, the depth of field will be throughout the entire depth of the frame;
• lens focal length- the smaller the focal length of the lens (for example, wide-angle), the greater the depth of field; on long-focus lenses, the depth of field is noticeably reduced;
• subject distance- the shorter the distance from the camera to the subject, the less depth of field, the greater the distance, the greater the depth of field.

Influence of the diaphragm on the depth of field.

As you can see from the pictures, a larger aperture gives a more blurred background.

5. The formula for calculating the depth of field

R1 - the front boundary of the sharply depicted space; R2 - rear boundary of the sharply depicted space; R is the distance in meters at which focusing is performed; f is the focal length of the lens (absolute, not equivalent), the value in meters is substituted into the formula; K is the denominator of the relative aperture of the lens (aperture number); z is the diameter of the permissible circle of confusion, for negatives of 24x36 mm format equal to 0.03-0.05 mm (the value in meters is substituted into the formula).

6. Aperture control

The primary role of the diaphragm is to control the depth of field. The aperture value is set depending on the goal. For example, when shooting landscapes, when the sharpness should be across the entire field of the frame, the optimal aperture value will be f / 11 - f / 16, when shooting a portrait, where it is necessary to focus on the subject, the value is - f / 1.2 - f / 2.5, in this case, the main object will be in the zone of sharpness, and the background will be very blurred. When shooting at a wide aperture, certain difficulties can arise, given that the zone of sharpness is only millimeters, a small change in the angle of the camera entails a shift in focus. What to consider. Chromatic aberrations (colour distortion) can appear at a wide open aperture, while closing the aperture too much results in diffraction (loss of sharpness).

7. Aperture and types of lenses

Lenses, depending on their specifications, have a different minimum aperture value. The fastest lenses are those with a fixed focal length - aperture number from f/1.2 to f/2.8. On zoom lenses, you can often see a threshold of f values, such as 18-55 f3.5-5.6. This means that at a focal length of 18mm, the minimum aperture value will be 3.5, at 55mm - 5.6. Advantages of high-aperture lenses: high-aperture optics allow you to work in poor lighting conditions without the use of additional equipment and at low ISO; a small number of lenses in the lens design, which ensures the best image quality; soft and beautiful bokeh wide open.

For reference: one of the fastest lenses on the market is the Carl Zeiss Planar 50mm f/0.7, commissioned by NASA for the Apollo lunar mission. On the ground, this lens "lit up" in some of Stanley Kubrick's films.

When purchasing a high-quality camera, you should not stop at standard settings. In this article, we will explain what a function such as aperture is required for and how to use its capabilities.

Physically, the aperture of a camera is petals that close the lens and let in a certain amount of light. The better the lens, the more petals it has, and the more beautiful the blur effect is achieved. We will not tell in words what photos can be obtained, but we will show everything visually.

These photos show children, and at first glance, the photos are almost identical. But in the first image, we clearly see the boy in the background, and in the second, the background behind the girl is all blurry. We note right away that this is far from the maximum degree of blur, and it is impossible to achieve the same effect manually (in Photoshop).

Now let's explain how the camera's aperture was set in both cases. In the first photo, the aperture is closed, as a result of which we see the whole picture clearly. In the second photo, the aperture is more open, which is why the boy is not visible. We have considered this and it is clear to us that with the maximum open aperture we get a blurry background, and with a closed hole - a clear one.

In almost all cases, the aperture on the camera is indicated as "f /" and a number, which indicates the degree of openness of the gap. At first, it will be difficult for you to remember all the values, so it is enough to know that the smaller the number, the more the background is blurred, and the larger it is, the better objects in the background are visible. The following picture shows the standard values ​​​​that are present even in ordinary soap dishes. You can see how the aperture changes depending on the indicators.

Even though the function is also available on compact cameras, it is impossible to achieve the effect of a blurred background on them. In order to understand the difference, it is enough to try out SLR and professional cameras in operation. Believe me, the differences in quality will be noticeable to the naked eye. And the number of functions, settings will pleasantly amaze you. Take your time to master everything at once and first deal with each parameter individually, and only after that choose manual mode and link them.

In the photo with the ladybug, you can clearly see that the diaphragm is fully open. Such a picture can be taken with any professional equipment, regardless of the brand - Nikon, Canon. The camera, most importantly, should be a SLR or professional.

In conclusion, it is worth saying that the aperture of the camera can focus attention on a certain object, highlighting it and blurring the background. The ladybug photo above clearly shows this effect, because you only see the insect, and the rest is not so important. The closed aperture of the camera is necessary when taking pictures of the street, landscapes, crowds, where it is required that the whole photo be in focus.

As you can see, not everything is as difficult here as it seemed at first, but before moving on to further study the art of photography, practice well at this stage.

Camera aperture (aperture)- a structural element of the camera lens, which allows you to change the amount of light passing through the lens (), as well as set the necessary (Fig. 1).

Fig 1. - Camera aperture

The aperture of the camera affects the following parameters:

• photo brightness. The larger the aperture number, the lower the illumination of the matrix, film;
• depth of field (DOF). The larger the relative aperture, the smaller the depth of field and, as a result, the greater the effect;
• image quality. A fully open camera aperture allows edge rays to pass through the lens, which can appear as aberrations. At the same time, too small a camera aperture is also undesirable due to light diffraction at its edges. Both defects affect the decrease in image contrast (Fig. 2). In this regard, the optimal value should be selected - the middle of the range of possible aperture numbers of the lens.

Rice. 2 - Influence of aperture on image contrast

To quantitatively characterize the aperture parameter, the concept " relative lens aperture» is the ratio of the diameter of the entrance pupil (D) to the rear focal length (f ′) (Fig. 3).

Where can you express the value of k - aperture value:

where D is the diameter of the entrance pupil - the aperture of the camera in millimeters;

f ′ is the distance from the main back plane H′ to the back focal plane in millimeters.

Rice. 3 - Relative aperture of the lens

F-number

Aperture number - inversely proportional to the relative aperture, which determines the degree of reduction in the aperture of the camera; displayed in the f-stop scale.

Each next value on the scale changes the relative aperture to the root of two times (in one step), while reducing the illumination of the light-sensitive element by exactly 2 times. Some cameras have a wider range of values, half or third step values ​​are allowed (Fig. 4).

The INCREASING the aperture value, the SMALLER the aperture of the camera. The f32 value corresponds to the smallest relative aperture, the light passes the least (Fig. 5).

Rice. 4 - Scale f-values
Rice. 5 - Aperture of the camera. F-number

Camera aperture. Setting

The aperture of the camera in the process of shooting can be selected automatically, depending on or set manually.

Aperture is set manually in Aperture Priority (Av) or Full Manual (M) modes. This setting allows you to adjust the depth of field (perhaps the most important factor) and control the "lens pattern" - bokeh (luminous dots that did not fall into the depth of field (Fig. 7)), vignetting, some distortion, swirling, etc., which can be used for artistic purposes.

It is easy to guess that the design of the lens depends very much on the choice of the lens itself, its design, optical design, materials, the number of aperture blades and the relative aperture value. This is what makes many photographers experiment with Soviet lenses, buy more expensive lenses with a larger aperture.

To change the value of the relative aperture of each individual camera, it is worth reading the user manual, as different manufacturers design the aperture value setting differently.

Camera aperture. Structure

A modern camera iris diaphragm consists of the following devices:

• actually the iris diaphragm of the camera;
• jumping diaphragm device;
• diaphragm repeater.

Camera iris diaphragm(Fig. 6) consists of several (most often 6-9) rotary blades 1, which are driven by a special ring 2 on the lens barrel or by an electric drive 3 controlled by the camera. When the aperture is open, the petals form a round hole, and when partially closed, they form a polygon 4. The shape of the polygon is affected by the number of aperture blades: the more there are, the more rounded it is, which in turn affects the appearance of the bokeh (Fig. 7).

Rice. 6 - Aperture of the camera. Design.
Rice. 7 - bokeh

Jumping diaphragm- the aperture control system in modern SLR cameras, which abruptly closes it to a given aperture value when the shutter is pressed. Thus, before shooting, the image is projected at the maximum aperture, which allows for the most convenient framing and precise focusing.

- the mechanism of the camera (button or lever), which allows you to forcibly close the aperture before pressing the shutter to the specified value. Used to check the adjusted depth of field before shooting. It is located on the left or right side near the lens (Fig. 8).

Rice. 8 - Diaphragm repeater

Outcome

Practical application of the camera aperture

• The aperture of a camera, like , is one of the parameters for adjusting the exposure of an image. Affects the depth of field, image quality;
• the larger the aperture value, the smaller the aperture of the camera in diameter (the entrance pupil);
• to achieve more bokeh, you need to open the aperture wider (f1.4 - f2.8);
• the optimal value for portraits is the maximum open aperture (f1.4 - f2.8) of the camera for strong background blur, beautiful bokeh. For landscape photography, f11 - f16 is optimal. For studio f8 - f9;
• checking the set aperture value in the viewfinder is carried out by a special button / lever - aperture repeater, which is located near the camera lens.