Lens aperture what. Exposure Basics

What is a diaphragm? In photography.

Short definition

The aperture is a structure inside the lens consisting of thin blades. By opening and closing the aperture you can control 1) the amount of light passing through the lens; 2) angle of refraction of light rays (depth of field).

You can see the aperture very well with fast prime lenses, such as, for example. If you want to see the aperture blades of your lens, then turn on your camera, select manual mode, select an aperture value of 14 and click on the depth of field preview button, which is usually located next to the lens. At the same time, if you look through the front lens, you should see the petals move when you press the button. If you don’t yet know how to set up manual mode on your camera, change the aperture, or don’t know where the depth of field preview button is, then you should read the user manual.

1. Aperture and brightness of the photo. Exposition.

The wider the aperture is open, the more light enters the sensor and the brighter the photo turns out. The further the aperture is closed, the less light hits the sensor and the darker the photo turns out. Thus, aperture is one of two ways to influence the brightness of a photograph. The second way is to change the shutter speed, or the amount of time the camera shutter is open and light hits the sensor.

2. Aperture and depth of field.

The size of the aperture opening determines the angle of refraction of light rays. The depth of field depends on the latter, one of the most important characteristics in photography. How bigger hole aperture, the shallower the depth of field in the photograph. The smaller the aperture, the greater the depth of field in the photograph.

When shooting a classic portrait, a large aperture is used. For what? Then, to emphasize the most important thing in the photo - the person’s face, and leave everything else blurry background so as not to distract. Depth of field at portrait photography maybe up to half a centimeter, this is quite enough. Although in this case the tip of the nose and ears are no longer in focus, so you should choose the focusing point very carefully. When you photograph a person, the focal point is always the eyes.

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How to set the aperture correctly.

Stops and aperture values. To make it easier for you to shoot.

About what a diaphragm is.

The aperture can be adjusted to suit you. To make it easier to change the aperture hole, you should use special steps for the camera aperture - feet. The concept of stops is also used in conjunction with shutter speed, but we will talk about this next time. Each stop of aperture lets in half as much or half as much light as the next.

Each stop has its own aperture value. They usually look like this:

The photo above shows the most common aperture stops. There are lenses with larger apertures (f/1.4, f.1.2) and smaller ones (f/27, f/32), but this is rare.

If you are trying to adjust the aperture on your camera (if you are unsure how to do this, be sure to read your camera manual), then you will of course notice that the aperture changes at specific values, but the numbers may vary. Between the full stops there are still other numbers. This is because on modern digital cameras the aperture can be adjusted much more precisely than using full stops. Usually in the camera menu you can choose whether you want to adjust the aperture using full stops or not.

Full feet

f/4.0

f/5.6

f/8.0

f/11

f/16

f/22

1/2 foot

f/4.0

f/4.5

f/5.6

f/6.7

f/8.0

f/9.5

f/11

f/13

f/16

f/19

f/22

1/3 foot

f/4.0

f/4.5

f/5.0

f/5.6

f/6.3

f/7.1

f/8.0

f/9.0

f/10

f/11

f/13

f/14

f/16

f/18

f/20

f/22

Aperture values can be confusing at first because higher value denotes a small aperture and vice versa. For example, 4.0 means a larger aperture than f/11.

How less value aperture (the larger the aperture itself), the shallower the depth of field.

When taking your first steps in the field of photography, difficulties often arise not only with building an exposure, but also with understanding the parameters that determine a high-quality image.

Aperture is one of the three main parameters that affect the exposure of a frame. Therefore, without understanding the operating principle, design and settings of this parameter, it is quite difficult to create high-quality professional-level photographs. For correct use parameter and switching at the right time, you need to understand what aperture is in a camera.

Understanding Aperture

In order to simplify the understanding of why an aperture is needed and what it is, it is often also called an aperture, relative aperture or aperture ratio; an analogy can be drawn with the human eye, or rather the pupil. The more dilated (open) the pupil, the greater the flow of light the retina can perceive.

To build the exposure of a professional photo, three factors must be taken into account: aperture, ISO and shutter speed. Changing the aperture value controls the amount of light that the sensor or film receives. This parameter changes depending on the shooting subjects, conditions, lighting, and the desired result. Also different indicators used to achieve special artistic effects.

However, it is important to remember that the most open hole allows more light to pass through, while a more closed hole allows less light.

What is aperture and how is it arranged in a camera?

To determine the aperture, a special aperture scale is used. Yes, the camera display shows the F/ indicator, followed by a certain digital designation. This parameter characterizes how wide the open aperture is. The number is opposite to the opening level of the hole, that is, than less number after the letter, the more open the aperture is. In order not to get confused in this pattern, it is important to understand the principle of operation.

The diaphragm row looks like this:

The transition from one value to another is considered one step. It is worth noting that one step changes the amount of light perceived by the matrix by half. Modern cameras also make it possible to set intermediate values - thirds or half, to obtain greater clarity.

Aperture structure

A modern diaphragm (iris) has the following components:

Repeater;
Jumping aperture;
Iris diaphragm.

Iris - includes several curtains (1), often from six to nine. They are brought into a movable state by a ring (2) located on the lens, or by an electric drive (3).

Diaphragm design

If the diaphragm is completely open, the hole has a round shape, and when closed, it has a polygon shape (4). This shape is influenced by the number of curtains, that is, if there are more of them, then the edges are more rounded, which also determines the shape of the bokeh.

Bokeh shape

Jumping - a symbol that controls the aperture, installed in modern models SLR cameras. It closes it abruptly to the selected aperture value at the moment the shutter clicks. Thanks to which the image is projected before shooting with the hole open, this affects the convenience and quality of focusing.

A repeater is a special device with which you can forcefully close the hole immediately before descent to the desired value. Most often used to check depth of field before shooting.

What does the aperture in a camera affect?

DOF – depth of field of the imaged space;
The amount of light transmitted by the hole onto the matrix;
Image brightness and contrast;
Image quality.

Impact on depth of field

In addition to luminous flux, aperture also affects depth of field. When the F index is small, then the depth of field will be small; if the F index is large, then the sharpness will be large. This is a fairly important tool for controlling the point of attention in the photo.

It is important to know how to use it correctly this opportunity To create boring accents, for example, when shooting portraits, you need to focus directly on the person, while leaving the background blurred. Photographers involved in macro photography especially delve into their understanding of depth of field settings; for such shots, a closed aperture is always used and the depth of field increases significantly.

Example of photography at different apertures

Modern cameras allow you to focus on an object even with the aperture as wide open as possible. At the time of shooting, the camera automatically closes the aperture to the required value. To preview the image in pinhole mode, you need to use the aperture repeater. This makes it possible to view in the viewfinder what it will look like after closing the aperture.

Image quality and aperture ratio

Aperture - Controlling the aperture setting is used to achieve a sharper image. Based on practice, maximum image sharpness is achieved when using average aperture ratios. This principle applies to all camera lenses.

If the aperture value is too high, then unwanted artifacts in the form of vignetting or aberrations may appear in the frame, if the aperture is too small, there is a significant decrease in sharpness.

A smaller aperture increases image contrast. The large aperture makes it possible to view using an optical viewfinder. If the F value is below 5.6, then you can only view through the optical viewfinder under good lighting conditions. Larger apertures will make images appear more saturated and vibrant, thanks to smoother transitions from dark to lighter areas.

Effect of aperture on bokeh

Bokeh and aperture are directly related. The best bokeh is achieved with the maximum open hole, the shape of which is as close to round as possible. If the aperture is closed, the hole has the shape of a polyhedron, which is clearly visible in the blurred area. Such polyhedra are usually called washers or nuts.

Budget versions of lenses suggest Not large number There are a maximum of six diaphragm blades, resulting in figures in the blur zone that resemble the structure of a nut. At a special price are lenses that are capable of creating circles of the correct shape due to a large number of aperture curtains. Modern models do not differ in the large number of curtains, but they are created in a more rounded shape, due to which the hole has the desired shape.

The influence of aperture on exposure

As the diameter of the hole changes, the exposure also changes. When the aperture is wide open, the sensor is exposed more strongly and the image appears brighter. To clearly demonstrate the effect, several pictures were taken at the same settings, but with different apertures.

Aperture F/2

Aperture F/4

Aperture F/8

Aperture F/22

For these frames the following parameters were set: shutter speed 1/400, ISO 200, flash turned off, aperture varied from F/2 to F/22.

How to choose the correct aperture value in a camera?

How the diaphragm works and what it affects is already clear, but how to control this parameter depending on the situation remains to be figured out.

There are no clearly established rules that indicate that it is necessary to use exactly this value and not one step differently. Each photographer individually selects this indicator depending on what he is shooting, why and under what conditions. However, to make it easier to understand at first, you can use some general tips.

If you plan to take photographs in low light conditions, then the f/1.4 aperture is excellent. however, it is worth remembering that with this indicator a rather small depth of field will be established. Ideal for shooting small objects or creating soft focus when needed.

The f/2 hole diameter is used similarly.

Also in low light conditions f/2.8 is used. Well suited for photographing portraits, as it achieves a depth effect that covers all faces, without focusing solely on the eyes.

The minimum aperture value at which decent shots of people are obtained is f/4. In this case, a limitation is set on autofocus operation.

If you are going to photograph two objects (people), then it is best to use f/5.6. If you need to take photographs in low light conditions, it is best to use an additional flash.

If removed big company people or several objects that must be in focus, then it is optimal to use f/8, this value provides good sharpness.

The vast majority of lenses are sharpest at f/11, making this mode well suited for portrait photography.

When shooting in bright conditions, it is best to use f/16, then a greater depth of field is established.

For landscapes or city photography, f/22 works well. There is no special focus on the foreground when using this value.

Knowing the basic principles of operation and aperture settings, even a novice photographer will be able to correctly set the exposure and get a high-quality photograph with different conditions shooting.

Everyone loves taking photos with their cell phone, but the built-in camera in everyone is different, so it's important to understand what each specification means. Then you choose a smartphone whose camera will satisfy your needs.

In this article, we'll delve into the meaning of many of the features so you can judge the camera's capabilities by reading the description or technical specifications review.

Diaphragm

The lens aperture is the opening through which light passes to the sensor and is designated by an F number (for example, f/2.0 or F/2.8). The smaller the aperture number, the larger the aperture and the more light passes through the lens, and the better the camera's performance when shooting in low-light conditions. The F number you see in the specifications is the maximum possible meaning aperture for a given focal length (more on focal length below).

For example, if a camera shoots at F/5.6, it will capture less light than at F/2.0. The 29mm F/2.2 lens on the iPhone 6 is what you'd call a "fast aperture" lens, which means you can shoot at higher speeds. high speed shutter The higher the lens aperture (the smaller the aperture number), the better suited it is for shooting dimly lit scenes. Therefore, choose a camera that has the smallest aperture number (F/2.2 is better than F/2.8).

In zoom cameras such as Galaxy smartphones K Zoom and Galaxy S4 Zoom, most often you get two pairs of numbers with focal length. At the same time, sometimes they indicate a constant aperture, but this is more typical for conventional digital cameras, not for smartphones.

Camera in Samsung Galaxy The K Zoom is equipped with a 24-240mm F/3.1-6.4 lens. This is called variable aperture. The first aperture number (F/3.1) indicates the maximum aperture when shooting at the widest angle (24mm), and the second F-value (F/6.4) indicates the maximum opening of the aperture when shooting at the tele-end (240mm). When you zoom and change the focal length, the aperture also changes.

It is also important to note that in cameras with large sensors, the aperture value affects the depth of field. So at a large aperture you can get a small depth of field, thus making a beautiful blurred background, the so-called "bokeh". Unfortunately, with a small sensor, which in most cases mobile devices, such an effect is almost impossible to achieve.

Aperture F/2.8.

By increasing the aperture number to F/11, the aperture becomes smaller and the depth of field increases, as in the example below.

Focal length

The focal distance is the distance from the optical center of the lens to the image plane; in phone cameras this means to the image sensor.

When you zoom, the optical center of the zoom lens changes, so the focal length also changes. FR also tells us about the angle of view, which is especially important. For simplicity, look at the equivalent focal length lens that takes into account the size of the sensor and gives you a 35mm equivalent FR. This indicator can be compared among different cameras.

The equivalent focal length tells you how wide the lens is. You can use this converter to understand what viewing angle we are talking about for a certain FR in 35 mm equivalent. The shorter the focal length, the wider the field of view.
So, for example:

iPhone 6/iPhone 6 Plus: 29mm (35mm equivalent)
Galaxy S5: 31 mm ( in 35 mm equivalent)

We can say that with the iPhone 6 and iPhone 6 Plus the field of view is wider, since 29 mm translates into 73.4 degrees, and 31 mm into 69.8 degrees.

With a shorter focal length, the camera can capture a wider area of the scene (vertically and horizontally). This is very convenient for shooting group shots, interiors, architecture, selfies, etc. That's why smartphone manufacturers endow the lens with front camera shorter focal length - to make it more suitable for self-portraits.

Lenses with a fixed focal length are called “primes”. This means that the camera does not zoom.

Galaxy Zoom smartphones have a variable focal length. For example, the Galaxy S4 Zoom is equipped with a 24-240mm F/3.1-6.4 lens. So 24mm is the focal length at the wide angle and 240mm is the focal length at the tele end. Of course, the aperture, as we mentioned above, is maximally open at the wide-angle position and minimally at the tele end.

Video by Mike Brown.

By the way, optical zoom is calculated by dividing the maximum focal length by the shortest. For example, in the case of the S4 Zoom, we divide 240 by 24 and get 10. In other words, the S4 Zoom has 10x optical zoom.

Sensor size

Sensor size plays a key role in camera performance. It is generally accepted that the larger the sensor, the higher the image quality. This is almost always the case. Manufacturers can apply more technological advances to a large sensor that are impossible or expensive to implement in small sensors. However, among the extremely important sensor specifications is the pixel size.

Pixels are measured in micrometers (μm) or microns (μ). Some smartphone manufacturers provide this indicator because everything more people understand the impact of pixel size on image quality and low-light performance.

How larger size pixel (photodiode, pixel aperture), the higher its ability to collect light.

You may find two cameras with the same size sensors but different resolutions. Here you need to decide whether you choose a low resolution with large pixels (for example, HTC One UltraPixel) or more high resolution, but with smaller pixels. Different cameras will have different sensor sizes and resolutions.

You may end up with a camera with large pixels that will not perform as well in low light as another camera because of the importance of sensor technology and image processing.

For example, sensors with BSI (Back Side Illuminated) technology use unique design, significantly increasing sensitivity to light. In a BSI sensor, the wiring responsible for transmitting data is located behind the light-sensitive area, allowing manufacturers to create small sensors with a large number of pixels. On FSI (Front Illuminated) sensors, the wiring is located in the front, taking up space where large photodiodes could be placed.

New generation sensors are demonstrating their superiority over earlier ones, and sensor technology continues to improve. The HTC One UltraPixel's 2.0 micron pixels don't always result in better low-light performance than sensors with smaller pixels. Currently, the first place is occupied by the iPhone 6 Plus with an 8 megapixel sensor and 1.5 micron pixels on DxOMark. TheHTC One M8 is in 18th place, significantly inferior even to the camera in the Samsung Galaxy S5 (3rd place), which has a 16-megapixel sensor with 1.12 micron pixels.

The size of the sensor, in conjunction with the characteristics of the lens, affects the depth of field. At the same aperture, a larger sensor will allow you to achieve a shallower depth of field, that is, more pronounced bokeh. The effect of a defocused background will help to highlight the subject from the background elements.

To get a more blurred background, you need a smartphone with a large camera sensor and a large aperture.

The size of the sensor is indicated in the list of specifications, it can be 1/2.3", 1/2.5", 2/3", etc. This means that this is its diagonal, but it is not easy for everyone to compare the sizes of sensors in this way. You can contact go to the online sensor size comparison tool cameraimagesensor.com or open the Wikipedia article, which lists the most popular sensor types with their equivalent width and height in millimeters.

You can see that the Nokia Lumia 1020 has a comparatively very large sensor (2/3-inch = 8.80x6.60 mm); Nokia Lumia 720 (1/3.6-inch = 4.00×3.00 mm).

Next time you're shopping for a smartphone, when looking at camera specs, be sure to take a look at the pixel size and sensor dimensions. Most modern camera phones are equipped with BSI sensors. Some have more advanced technology than others.

Image stabilization

Image stabilization is one of the most important aspects of many modern phone cameras. There is digital and optical image stabilization. With optical image stabilization, the camera compensates for hand movements and shake by moving the lens elements to the side, opposite direction movement, resulting in clearer images.

Images from a patent application from Apple that describes a method for integrating optical stabilization into miniature cameras.

When shooting handheld, there are inevitable small movements that can lead to a blurry photo. If you place your phone on a stable surface, this concern will disappear. Nose mobile phone Most of the time you shoot handheld. To get a sharp image, the rule of thumb for shutter speed is that the denominator of the shutter speed should be at least as large as the 35mm equivalent focal length number. That is, to get a sharp image when shooting with a 30mm lens (equivalent), you need to set the shutter speed to 1/30 sec.

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

Imagine a completely dark room in which there is a window with black glass through which no light penetrates. 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, the whole room will be filled with light. In both cases the window was open, but the lighting was completely different. In a camera, the role of the window is played 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 open determines many of the characteristics of future photography. Many, but not all, since the diaphragm is not the only element taking part in this.

What does the diaphragm look like? This is a damper assembled from so-called “petals”, which, rotating in a circle, form holes of different diameters (see attached photo). Remember the window analogy? The size of the round hole that the movable petals form is similar to the opening of a window. The diaphragm may consist of different quantities petals, and this also plays a role in constructing the image.

How to use aperture

In the camera settings and on the lens markings, aperture characteristics are indicated using the letter f with the values assigned to it numerical values, 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, the f/1.2 value means that the aperture is wide open and a lot of light will enter the matrix, and f/16 means little. When choosing a lens, it is important to pay attention to the f/ marking. The lower its value (starting from the standard f/3.5), the better.

When the aperture is wide open, a large amount of light enters the sensor. This allows for low-light shots without the use of flash or long shutter speeds. By the way, this is a time period that determines the time during which the camera shutter remains open, letting light into the matrix. If we go back to the window analogy, this is the time you will keep it open.

In addition, the opening width of the aperture determines the depth of field. To put it simply, 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, but the background is blurred. Or only a small detail of the subject is in focus, while everything around remains blurry. In photography, this beautiful effect is called “bokeh effect.”

With maximum open apertures, you can achieve focusing on the smallest details, and all other light sources in the picture will be blurred into multi-colored round dots. Now is the 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 closed aperture provides greater depth of field, i.e. more objects will be in focus. This is widely used in photography where all the details are needed, such as architectural or landscape photography.

Also, these aperture settings should be used when shooting with a tripod and long shutter speeds. Not in low light, but at night, when the number of light sources is minimal. The narrow aperture allows you to take clear, blown-out photos that show all the details.

Knowing the theory, it is important to experiment with different meanings diaphragm independently. Having seen the difference in the pictures, you can learn how to choose the right value for different conditions and always achieve excellent results.

Greetings, dear reader, in this article we will deal with the following:

How does the camera aperture affect it?
What is the designation for aperture?
How to set the aperture on a camera?

What is a camera aperture?

So, camera aperture- this is a mechanism that regulates the amount of light entering the camera matrix. The aperture itself is located in the lens, and is one of the main characteristics of the lens. If we draw an analogy, the diaphragm is like the pupil of the eye, in bright light the pupils are reduced to reduce the amount of light transmitted, in the dark the pupils are enlarged to receive more light, which means it is better to see in the dark.

1) Set in the settings: Bright sun, Aperture priority, ISO 400

2) We change only the aperture value, starting from f 2.8. We take a photo with each new aperture value and watch how the background changes. In this exercise, our goal is not to get good shot, and see how the background blur and shutter speed change when the aperture changes.