Publication date: 19.01.2015

How does the size of a camera's sensor affect the viewing angle of the lens?

This is the third part of a lesson about camera lenses. In the first and second parts, we got acquainted with the structure and main characteristics of lenses. We talked about the fact that the viewing angle and focal length of the lens are the main characteristics in previous lessons. We already know that these characteristics are interrelated:

The shorter the focal length of the lens, the wider its viewing angle.

The longer the focal length of the lens, the narrower its viewing angle.

When a person uses his own camera, over time he gets used to the fact that at certain focal lengths, his lens gives one or another viewing angle: it “brings closer” the subject being photographed stronger or weaker. Will these relationships between focal length and viewing angle remain the same or change if you change the camera? Today we will find out. Often, when discussing photographs, photographers say: “this picture was taken at such and such a focal length,” thereby characterizing the viewing angle at which the image was taken. Even under photographic examples in our articles, the focal length of the lens with which these images were taken is often indicated. How do you know what focal length on your camera corresponds to the same viewing angle? How can you take the same photo with your camera?

We have to figure out how the viewing angle of the lens will depend on the model of your camera, get acquainted with the concepts of “crop factor” and “equivalent focal length”.

Excursion into history

Previously, in the film era, 35 mm film was widely used - ordinary photographic film, familiar to every person. It was used everywhere, from the simplest compact cameras (perhaps everyone had a film “soap box”) to serious professional equipment. Since all devices had the same area of the photosensitive element (film frame), lenses with the same focal length on all devices gave the same viewing angle. For example, on any camera that works with 35 mm film, a lens with a focal length of 50 mm had a viewing angle of 45°. Let us remind you that modern full-frame digital cameras also use a sensor the size of a film frame - 24x36 mm.

Lens viewing angle and sensor size

Today the situation has changed. Matrixes in digital cameras come in different sizes.

Therefore, with the same focal lengths of the lens on different cameras, the viewing angle will also depend on the size of the camera matrix. Let's look at the diagram:

It turns out that if on a full-frame matrix (or on a film frame) a lens with a focal length of 50 mm provides a viewing angle of 45°, then on an APS-C format matrix it is already 35°. On a Nikon 1 system camera with an even more compact 1” format sensor, the same lens will provide a viewing angle of only 15°. The smaller the matrix in the camera, the stronger the lens with the same focal length will “zoom in”. The same lens, when installed on different cameras, will produce a completely different picture. This must be taken into account when choosing optics.

Since today different cameras have matrices of completely different sizes, it is easy to get confused about what viewing angle a lens with a particular focal length will give on a particular camera.

Old-school photographers, accustomed to working with film photographic equipment and classic focal lengths, clearly associate them with specific viewing angles. To understand what focal length corresponds to a particular lens viewing angle on modern devices, two concepts were introduced: crop factor and equivalent focal length.

Equivalent focal length (EFL)

This characteristic is not needed by beginners, those who bought their first camera - the numbers of the equivalent focal length will not tell them anything. But experienced photographers who are accustomed to film photographic equipment will find this characteristic useful. It will also be useful to those who are thinking about buying a new camera with a matrix of a different size and want to choose the optics that are suitable for it, and find out how their old lenses will work on the new camera.

Equivalent focal length allows you to find out what focal length a lens with the same viewing angle would have on a full-frame (or film) camera. This characteristic allows you to compare lenses of all types of cameras, including compact ones. In the characteristics of a lens not designed for a full-frame camera, you can often find the item “equivalent focal length” or “35mm equivalent focal length.” This point is needed so that the photographer can figure out what viewing angle this lens will give. For example, for a lens with a focal length of 50 mm mounted on a camera with an APS-C matrix, the equivalent focal length will be 75 mm. The tiny 4.3mm focal length used in the compact camera lens has the same field of view as a 24mm lens at full frame.

How to calculate the equivalent focal length yourself? To do this you need to know the crop factor. This is a conditional multiplier that reflects the change in viewing angle of the lens when used with smaller matrices. This multiplier is derived by comparing the diagonals of the matrices of digital cameras with a 24x36 mm film frame. The word “crop factor” comes from the English words crop - “cut” and factor - “multiplier”.

For example, the diagonal of an APS-C format matrix is approximately 1.5 times smaller than a full-frame one. So the crop factor for an APS-C matrix will be 1.5. But the diagonal of the Nikon CX format matrix is 2.7 times smaller than the full-frame one. Therefore, its crop factor will be 2.7. Now, knowing the crop factor, we can calculate the equivalent focal length for the lens. To do this, you need to multiply the actual focal length of the lens by the crop factor. Let's say we need to know the equivalent focal length for a 35mm lens if it is mounted on a camera with an APS-C sensor. 35x1.5=50mm. So, the equivalent focal length of such a lens will be 50 mm. That is, on an amateur DSLR, a 35 mm lens will behave in the same way as a classic “fifty-kopeck” lens at full frame.

In further lessons we will study what lenses are used when shooting various scenes, we will indicate their focal lengths for both cameras with an APS-C matrix and for full-frame cameras.

Dimensions of matrices and crop factor of Nikon photographic equipment

Modern Nikon system SLR and mirrorless cameras use only three standards of matrices of different sizes. They are easy to understand.

Full frame sensors(Nikon FX). They have a physical size of 36x24 mm, that is, they are equal in size to a frame from 35 mm film. Most modern lenses are designed for such cameras. And on them they can reveal their full potential. Among modern Nikon devices, the following are equipped with full-frame matrices: Nikon D610, Nikon D750, Nikon D800/D800E, Nikon D810, Nikon D4/D4s, Nikon Df. Since the matrix of such cameras is equal in size to a film frame, then the concept of crop factor and EGF is not needed for such devices.

APS-C format matrices(Nikon DX). They have a physical size of 25.1x16.7 mm and a crop factor of 1.5. Such a matrix is slightly smaller than a full-frame one, but much cheaper. Such matrices are sometimes called “cropped” (cropped). This matrix size is used by almost all digital SLR camera manufacturers. Among modern Nikon devices, Nikon D3300, Nikon D5300, Nikon D5500, Nikon D7100 cameras have APS-C matrices. You can still use full-frame optics with them, however, all lenses will “zoom in” much more strongly, which is not always convenient, because some lenses are designed for a very specific type of shooting and their loss of the required viewing angle does not allow them to be used for their intended purpose. First of all, this applies to wide-angle, portrait and reportage optics. Full-frame wide-angle optics lose their main advantage - a large viewing angle; full-frame portrait lenses on crop begin to zoom in too much, and it becomes difficult to shoot with them; you have to move very far away. For example, if you install a classic portrait lens with a focal length of 85 mm on a cropped camera, you will have to move 5-7 meters away from the person being photographed in order to shoot at least a waist-length portrait. Full-frame reportage optics (primarily zoom lenses with a focal length of 24-70 mm) have awkward viewing angles on the crop, which are not very suitable in practice for fast, dynamic reportage shooting.

To create lenses suitable for these tasks, specially designed lenses are produced for crop. In the Nikon system, such lenses are marked with the letters “DX” in the name. Since such lenses are designed for use on a smaller sensor, they themselves become more compact and cheaper than their full-frame counterparts.

For the same reason, they will not be able to work correctly on full-frame cameras. What happens if you install a “cropped” lens on a full-frame camera? Unlike Canon cameras, Nikon has this feature. In this case, you will get very strong darkening at the edges of the frame. By the way, modern full-frame Nikon cameras can recognize “cropped” optics if they are installed, and they automatically crop the frame to the size of the APS-C matrix. This setting can be turned on or off in the camera menu.

NIKON D810 / 85.0 mm f/1.4 SETTINGS: ISO 80, F1.4, 1/1250 s, 85.0 mm equiv.

When working with a camera, it is very important to understand what the focal length of a lens is and how to work with it. Every photographer should learn to realize their creative potential by using focal length as one of the tools in creating a photograph. In addition, for every person involved in photography, it is important to work comfortably with the camera, so you should decide which lenses are most suitable for you.

1. What is focal length

Focal length (FR)- this is a complex mechanism that affects various characteristics of the future frame. Without going into details, FR affects the image scale. The higher the focal length number, the larger the objects in the photo will be and they will be closer together. Focal length is a numerical reflection in millimeters of the distance between the camera sensor and the optical center of the lens (convergence point). You can clearly see the principle of measuring DF in the diagram:

2. Focal length ranges. Their application

The focal length is divided into:

Ultra wide angle 12-24 mm

These lenses are not used often. They capture a very large space and at the same time greatly distort it. Such a large girth is unusual for the human eye, so the pictures may seem strange to many. Such lenses are used when shooting large objects from a short distance or in architectural and interior photography in confined spaces. Such lenses are not suitable for photographing people, as they greatly distort the perspective and, as a consequence, the body structure and facial features.

Wide angle 24-35 mm

I call these devices kit lenses. The 24 mm FR produces virtually no distortion, although it is still noticeable to the naked eye. Such lenses are most often used by journalists in reportage and documentary photography. This lens has a wide frame angle, so it can fit many objects into the scene. In this case, distortions practically do not appear.

Standard 35-70 mm

These types of lenses with an FR of 45-50 mm have approximately the same coverage as the human eye. Peripheral vision is not taken into account. Standard lenses are the most common and are used for a wide variety of purposes.

“Fifty dollars” is the name of a lens with a fixed focal length of 50 mm. Its aperture is most often f1.8. Lenses with a fixed focal length provide higher-quality images than zoom lenses due to the fact that they have a larger aperture ratio and do not spread out over several focal lengths.

Telephoto lenses 70-105 mm

After 105 mm, long telephoto lenses begin, as well as primes for portrait photography (approximately 85 mm). Telephoto lenses are great for portrait photography. They do an excellent job of separating the foreground from the background without flattening or distorting the picture.

Super telephoto lenses 105-300+mm

These lenses are suitable for photographing distant objects. This could be mountains, buildings, people in the distance and wild animals. Such lenses are not suitable for landscape photography, since at a focal length of more than 300mm they greatly flatten the perspective.

3. Perspective of the photo and its PD

This section will describe the effect of focal length on perspective. The picture below shows three objects that are 10 cm apart from each other.

4. Crop factor

If you have a camera with a crop sensor, then you should know what the crop factor is. For example, if you take full-frame optics and install it on a camera with a crop sensor, the image will seem to be cut off at the edges. The trim factor is approximately 1.6. For a specific example, let's take a lens with a focal length of 35 mm. The photographs he takes with a camera with a crop sensor will look the same as photographs taken with a full-frame camera with a 50mm lens.

More details on how it works are shown in the diagram:

Buying a lens made specifically for cropped cameras will not solve this problem, since it is generally accepted to specify a focal length that will be relevant for a full-frame camera.

For example, two more pictures taken with a camera with a crop sensor. One photo was taken at a focal length of 24 mm, and the second at 300 mm.

Based on materials from the site:

The lens is the most important element of any camera. And focal length is the most important characteristic of a lens. However, novice amateur photographers experience complete confusion with this characteristic. They cannot understand: for example, a lens with a focal length of 24-70 mm on a full-matrix camera - is it good or bad? Is 15-44 mm on a “cropped” DSLR normal or not enough? Is 7.1-28.4 mm on a point-and-shoot camera quite small or is it still ok? Well, let's figure out what the focal length of a lens is and what its different values mean. A lens is a system consisting of several lenses. The image of the object being photographed enters the lens, is refracted there and reduced to one point at a certain distance from the back of the lens. This point is called focus(focus point), and the distance from the focus to the lens (lens system) is called focal length.

Now let’s talk about what these or other focal lengths mean in practical terms. Initially, let’s agree that we are now talking about a lens designed for shooting on a full-matrix camera (in this article we talked about what a “full matrix” is). Let's take a purely practical look at the differences between frames taken with one focal length or another. We shoot from one point and change focal lengths from 24 to 200 mm. Focal length 24 mm.
Focal length 35 mm.
Focal length 50 mm.
Focal length 70 mm.
Focal length 100 mm.
Focal length 135 mm.
Focal length 200 mm.
Obviously, the shorter the focal length, the more is placed in the frame, and the longer the focal length, the closer the lens brings distant objects. Short focal lengths are used for shooting all kinds of images: landscapes, architecture, large groups of people. Long focal lengths are used for shooting, for example, animals and birds, for sports photography, when you need to catch some spectacular shot close-up. A focal length of 50 mm approximately corresponds to the viewing angle of the human eye (46°). Lenses with a focal length of less than 35mm are called wide-angle. With their help, it is convenient to photograph nature and architecture, however, it should be borne in mind that the wider the angle (smaller focal length), the greater the distortions caused by the laws of optics will be present in the photographs.
For example, if you shoot high-rise buildings with a lens with a focal length of 24 mm, then closer to the edges of the frame on the right and left the buildings will appear tilted - here is an example.
Lenses with a focal length of less than 20mm are called ultra-wide-angle lenses, and they distort the image very much. (There is also a separate type of lens with a fisheye effect.) Here is an example photo (from here) taken with a wide-angle fisheye with a focal length of 8 mm. Lenses with long focal lengths are called “long focal lengths”, and those with very long focal lengths are called “telephoto lenses”. In general, the classification there is approximately as follows: Lenses come with a fixed focal length (the so-called “primes”) and with a variable focal length (the so-called “zooms” from the word, bring closer). As a rule, lenses with a fixed focal length take better pictures (and are cheaper) than a zoom set to the same focal length. That is, for example, in general, a 24 mm wide-angle will provide better quality than a 24-70 mm zoom set to 24 mm. (There are exceptions, but we won’t get into those jungles now.) And now we come to a very important question. What is this strange focal length range of my Fujifilm X20, you may ask? It says 7.1-28.4 mm. Is it like a super mega extra wide angle? No. The fact is that when we talk about cameras with a cropped matrix, the physical focal length of the lens does not change (it cannot change), however, since much less fits into the frame on a cropped matrix, it turns out that the “angle of view” of the lens narrows, and Accordingly, for a given matrix the focal length will be different. Precisely “as if different,” because if the lens has a focal length of 50 mm, physically it will remain that way on any matrices. But the shots will be different. I'll explain now. Let's say we have a lens with a focal length of 50 mm. It forms a circular image, which, superimposed on the full-size matrix, gives us a full frame - there it is, marked in the illustration.
We put the same lens on a camera with a cropped matrix - for example, with a crop factor of 2. What will a frame taken with the same lens look like? It will appear within the blue rectangle in the illustration. That is, less. And less means the object will be closer, so it turns out that when shooting with a lens with a focal length of 50 mm on a camera with a crop factor 2 matrix, the focal length will be equivalent to shooting with a lens of 100 mm (50 mm times the crop factor) on the camera with a full-size matrix. The problem is that cropped camera lenses usually indicate the physical focal length of the lens. And in order to understand what these numbers generally mean, you need to multiply the specified focal length by the size of the crop - then you will get the numbers of the focal length (distances for zoom) in the equivalent of a full-matrix camera (35mm matrix) and you will understand what range of focal lengths is present in this camera Example. Fujifilm Finepix X20 camera, zoom range - 7.1-28.4 mm. The crop factor of this camera's matrix is 3.93. So we multiply 7.1 by 3.93 and 28.4 by 3.93 - we get a range (rounded) of 28-112 mm in 35 mm equivalent. In general, the most common range for a digital camera. Second example. Amateur DSLR with a kit lens. The lens has a range of 18-55mm. The crop factor of the matrix is 1.6. Multiply - we get 29-88 mm.

Good afternoon friends! We are gradually getting closer to the key concepts in photography (we are talking about), without understanding which further progress in learning photography and conscious shooting in general is unthinkable, and this is what gives good, stable results. Let me give you a quote about following the rules in photography:

Failure to follow this rule results in garbage.
The ability to follow this rule gives a reliable craft level.
The ability to break this rule produces masterpieces.

So, I believe that beginners should strive to master basic techniques and develop basic shooting skills (confidently shoot in manual mode, understand how to compositionally frame a frame, what to emphasize in a frame, how to process pictures...). And a confident base and experience will definitely bear fruit in the form of more interesting results, don’t even doubt it!)

Concept of lens focal length

Focal length is one of the most important characteristics of a lens. In short and simply, this parameter determines how close the image we can get. When choosing a lens, you should start there because your shooting style requires certain focal lengths.

I assume that you already have, which we discussed earlier. Pay attention to the following diagram of a SLR camera:

Here the red dotted line indicates the optical axis of the lens, in fact its center. Here we look at the camera with a cutaway lens, top view. If you turn the lens with the front lens towards you, mark (mentally, of course!) the center of the circle, then draw a perpendicular down from it and get the optical axis. The object being photographed is marked in green on the left. The red lines represent the passage of light through the lens.

Every lens has a lens that flips the image. The point where the rays intersect is called the optical center of the lens. In the figure it is marked by the point of intersection of the lines.

Hold your attention on this diagram for a short time and take a closer look. There is nothing complicated about it, you just need to get into it once.

Focal length is distance from the optical center of the lens to the focal plane (matrix). See schematic drawing above.

Lens developers know the exact location of the optical center. And the point that corresponds to the focal plane, i.e. matrix, can be identified by the designation of a circle with a straight line intersecting it on the camera body to the right of the wheel that switches shooting modes (on Nikon).

Naming. In the speech of photographers you can hear the following names:

focal length;
focal;
FR (abbreviation);
focal length (English equivalent);
FL (abbreviation for English equivalent).

How is focal length measured?

Dimensions in millimeters, mm. It's better to look at an example. Let's say we have a popular Nikon 35 mm f/1.8G AF-S DX Nikkor lens. The marking indicates 35 mm, i.e. its focal length is constant and is 35 millimeters. Don’t pay attention to the other characteristics for now, we’ll look at them when we talk about lenses.

Another example is the standard Nikon 18-55 mm f 3.5-5.6 GII VR II AF-S DX Nikkor kit lens. 18-55 mm is indicated here, the focal length is variable. That is, by turning the zoom ring on the lens, you can change it from 18 to 55 mm. Looking ahead, such lenses are called varifocal lenses or zoom lenses.

Popular misconception. Sometimes you hear that the focal length depends on something. This is wrong. As described above, focal length is a physical characteristic of the lens, which is intended by the designers. It does not change under any circumstances.

What does focal length affect?

Attention! We are approaching a critically important part of our conversation. If you understand what is discussed below, you will give yourself an excellent foundation for understanding composition, which is extremely important. If not... You can't help but understand! If anything happens, I am always at your service in the comments.

Parameters affected by focal length:

Viewing angle;
Image scale;
Degree of blur and depth of field;
Perspective (indirectly).

Let's look at everything in detail. Small conventions - in the article about matrices we looked at. There we talked about the fact that the larger the matrix, the wider the viewing angle. Here we will accept a certain matrix size and will consider all changes in parameters based on the fact that the matrix does not change. In order to avoid confusion in different focal lengths depending on the size of the matrix, an EFR (effective focal length) was adopted, which recalculates the focal length in the equivalent of a full-frame camera. We will talk about this in the next article about the crop factor. All the following examples are from a crop camera, i.e. if the same shots were taken with a full-frame camera, the viewing angle would be wider.

Effect of focal length on viewing angle

As the focal length increases, the viewing angle decreases, and vice versa, the shorter the focal length, the wider the viewing angle. Look at the examples - taken from the same point at different focal lengths.

We can conclude that:

The more surrounding space we want to capture in the frame, the wider-angle (with a shorter focal length) the lens should be.
Conversely, if you need to shoot a relatively distant object, then it is better to prefer a telephoto lens (with a long focal length).

Effect of focal length on image scale

In fact, this is related to the first point. The fact is that with a larger focal length, the object being photographed will appear larger in the final image. They say that such a lens will give greater magnification or a larger image scale.

Example - we stand at one point, without moving, and photograph a person at a distance of 10 m with a wide-angle lens with an 18 mm AF. We get a full-length photograph of a person and a lot of space around the edges. By changing the lens to another one, for example, with an 85 mm FR, we will also get a full-length image of a person, but now there will be less empty space around the edges, and the person himself will be larger. As a result, we will get an image on a larger scale.

The effect of focal length on the degree of blur

It is quite possible that you have already heard about this and know that the longer the focal length, the more blurry the background will be. This is why portrait photographers love telephoto lenses (long focal lengths). Look at the example of a toy to see how the blur changes:

It is worth mentioning that as the focal length increases, the depth of field (DOF) will become smaller, thereby forming blur. Just keep this in mind; we’ll talk about depth of field a little later.

Some beginners associate a DSLR (or mirrorless) with the possibility of strong background blur, which is what they do when they get their hands on such a device. In fact, blurring the background “into the trash” is not always useful. Yes, all our attention is concentrated on the object being photographed, but there is nothing else in the picture! In many cases, it is better to still have background details visible. And the correct choice of focal length plays an important role in this.

Effect of focal length on perspective

To begin with, what is perspective? This is the nature of the transfer of the ratios of the sizes of the object being photographed and other elements in the frame, its shape. Consider the following frame, shot at 17 mm (wide angle):

There are road barriers and houses in the distance. If you shoot with a wide-angle lens, you get interesting geometric relationships - the scale of the fence will be noticeably larger than the house on the horizon. This is unusual for the human eye, and allows you to build interesting compositional solutions.

In the second case, shot at 125 mm (telephoto focal length range), the difference in scale between the fence and the house will be smaller.

In general, when photographing objects from one place with different focal lengths the perspective will not change.

Focal length affects perspective only if objects that are close or far away fall into the frame. In the example above (1st photo) you can see that there is a fence in the frame located close to us. Being close to us, the fence is depicted large in the frame, and the houses seem small in contrast. Therefore, it seems to us that the perspective is stretched. Another example is if you shoot a distant object with a long lens, and there is another object much further away, it will seem as if there is a minimum distance between them and they are nearby. As they say, compressed perspective. This occurs due to the photographer’s very strong distance from the subject being photographed, and the difference in the scale of the photographed object and the very distant background is not so great. This can also be seen in the example above (2nd photo). The fence is far away, the house is very far away, but it seems as if the distance between them is not too great.

Wide-angle lenses with short focal lengths are great for landscape photography. However, they are not recommended for use when shooting portraits, because the shape of the face will be more elongated and look unnatural. They say that wide-angle lenses (small focal lengths) stretch out perspective, while telephoto lenses (long focal lengths) compress it. But this happens primarily not because of a change in the focal length itself, but because of the need to change distance between the subject and the photographer.

Shooting handheld at long focal lengths

Problem.

Can be considered an additional activity for those who want to know more) I propose to move on to a short photo discussion and consider a simple situation. In fact, it’s worth “scrolling” such thoughts in your head constantly; very quickly you will get used to doing it automatically.

Let's say you're shooting a close-up portrait in the evening on a camera with an APS-C matrix. It’s not sunset yet, but it seems that there may already be problems with the lighting, it’s not enough. The goal is to take a beautiful portrait with a strong background blur.

In fact, if you study photography from scratch and consistently read my articles (see), then you understand that your knowledge is not enough. But there’s nothing wrong with that - let’s reason with what we have and gradually expand the horizon of the unknown) Don’t worry, very soon the puzzle of knowledge will come together in your head. Just don't be lazy to think.

Recently we talked about the matrix, (ISO). So, at the same ISO on a camera with a smaller matrix (we are comparing cameras of approximately the same generation and manufacturer), the picture will be noisier. Usually the noise level of full-frame cameras is taken as the standard. It follows that it is very likely that our camera will be able to record less light with the same quality. Let me explain - when shooting with a full-frame camera at ISO 1600, we get an image of a certain noise level. When shooting on a camera with an APS-C matrix, in order to get the same noise level, we already need to shoot, for example, at ISO 400. This means that less light will get in, which is clearly not a good factor in our conditions.

We need to achieve a strong blur. This can only be done with a telephoto lens with a long focal length. The degree of blur depends on other factors (for example, the distance to the subject, aperture), but more on that later. Let's say we chose 105 mm. This is a fairly large focal length, and...

The longer the focal length, the faster the shutter speed you need to choose. This will compensate for shaking in your hands and get a clear, not blurry photo.

Excerpt? What? Again, we will look at it in detail soon. In short, this is the exposure time of the matrix, i.e. the time during which light hits the matrix after pressing the shutter button. Get used to the word “exposure”) Now we come directly to the problem of handheld shooting with a lens with a long focal length.

You can make a comparison - imagine that you are in school and you need to point to a small detail on the board. Which would be easier to do – with a short handle or a long pointer? Of course, with a pen. The reason is that when using a pointer, minimal deflection of your wrist will result in significant deflection of the opposite side of the pointer. Using a pen, even with a significant deflection of the brush, its opposite edge will not deflect so much. That is, when using a long object as a pointer, we need to clearly fix the position of the hand.

It’s the same in photography, only more complicated. Where we point on the board is our subject. The lens acts as a pen or pointer. Well, the hand remains the drive of this entire mechanism) It is important to understand that the lock here is our strong grip on the camera, a comfortable stand and a short shutter speed (we reduce the exposure time of the matrix). Even if our brush moves at a significant angle, the shutter will operate faster, and the matrix will no longer “see” this.

Let's say we shoot at a shutter speed that is long for these conditions. What's happening? Light from a point on a person passes through the lens and hits the matrix, forming the same point. Our hand trembled slightly, the camera moved upward, and light from another point on the person fell on the same point of the matrix. And at this time the matrix continues to be exposed. As a result, we get a blurry image, or, in common parlance, “stir”. If the shutter speed were shorter, the result of the shift would not be recorded on the sensor, and we would get a clear photograph.

So what's the answer? And it is very simple - you need to find a balance, the optimal ratio of all parameters. Minimize problems and achieve the best possible results. This reminds me of university times) This is what we will learn.

What to remember about focal length?

I think you already understand what it is and what it affects. Now briefly to repeat the basic information:

Focal length is the distance between the optical center of the lens and the camera matrix.
Often abbreviated as FR.
Measured in mm.
The focal length is determined by the lens designers and does not depend on the camera on which the lens is installed.
Affects the viewing angle and image scale, allowing you to “zoom out” or “bring closer” objects.
Affects the degree of blur and depth of field.
Affects the perspective of the image.
At longer focal lengths it is more difficult to shoot handheld.

Focal length greatly influences the final result, so it is important to learn to “feel” it and choose the right one for specific purposes.

I suggest you go outside and try to shoot, for example, landscapes with different focal lengths, while being at one point. And observe how objects approach, how geometric relationships change. Take pictures of nearby objects, for example, a tree branch. You don’t even have to shoot, but simply change the focal length (if you have a zoom lens) and observe the changes in the viewfinder.

Over time, you will become so accustomed to your camera and lens that you will be able to determine the approximate result without looking through the viewfinder.

Good luck and see you soon!

4 comments on What is focal length? What does it affect?

Hello, Vlad! I read your lessons on photography, I really liked the articles about the device of the camera, everything is consistent, clear and intelligible. Thank you for this presentation of the material, I will look forward to the continuation with interest :)
Maybe you can make a short announcement about what other topics we can expect articles on? And what materials do you think are useful for a beginner to learn? Otherwise there is so much, you won’t immediately understand what needs to be dealt with first)

Good evening, Ekaterina!
Thank you very much for appreciating my work, it’s always very nice to receive such feedback :) Motivates, because... I feel like this was useful to someone!

1. Regarding announcements, there are materials on the horizon about crop factor, aperture, shutter speed, ISO, exposure, dynamic range and... Perhaps I won’t reveal any more cards for now)

2. Regarding materials that would be useful for a beginner to study. First you need to understand at what point a person is, i.e. what he knows at the moment and where he wants to go (what results to achieve) and based on this, plan the optimal steps to overcome this path. Tell us in general terms what you know at the moment and what you are striving for (what genre of photography attracts you most and what works inspire you).

Generally speaking, in my opinion, a beginner needs to conduct an educational program for himself on critical aspects. These include the triangle of aperture, shutter speed, ISO, have an understanding of exposure, focal length, depth of field, shooting modes (shutter speed/aperture priority or manual, it’s better not to shoot in “Auto”) + basic aspects of composition. In general, having a superficial understanding of all this, I would further advise filming, filming, filming as much as possible.

At the same time, pay attention to the surrounding space from the viewfinder position. Go, for example, to work and, watching how the light falls on the flowers, think about what angle they would look best from, how you would frame them... In parallel with practice, close the gaps in the basic theory of photography, look at many photographs of other people and reflect on how and under what conditions they were filmed. I think the latter is very important. Try shooting in RAW format, you can even start right away, especially if you have editing skills. RAW provides tremendous editing capabilities, “forgiving” many mistakes.

You definitely need to learn how to process photographs - I’m not a fan of applying a ton of processing to the original frame, but I think that doing basic things (exposure compensation, noise reduction, sharpening, working with shadows/highlights, color correction, eliminating noise, etc.) should be done, i.e. To. give a noticeably better perception of the final photograph. For my part, I can recommend Lightroom.

And gradually move on to more advanced things, but by that time the “newbie” himself will be able to tell and show a lot of interesting things and he will definitely have an understanding of what to do and where to move next. For basic things, for example, I recommend reading the articles on Alexander Shapoval’s website, he explains them well. And don’t forget that practice is everything.

As for my plans, at the moment I have a desire to put together something like a textbook - a sequentially written manual, after reading which a beginner in photography could get comfortable, learn to get good results and critically approach the analysis of his / other people's photographs, the main thing is that learned to think. Plus he knew how to process his photographs, he could easily understand them when there were a lot of them and he simply loved photography)

It is difficult to describe this at once and takes a lot of time. But gradually materials in chronological order for study will be added to the Lessons section (for now only technical ones, about processing later) + periodically I make Friday Mood collections, where I thematically present the works of other photographers who inspire me and seem interesting.

P.S. To keep abreast of emerging materials, if you wish, I recommend subscribing to the email newsletter or VK group in the upper right corner of the site. And, of course, you can feel free to ask any questions in the comments or here. I will try to answer if possible.

It is often mistakenly believed that focal length- this is the distance to the focusing object. This is, of course, not true. Focal length- one of the most important characteristics of the lens, which determines its viewing angle, that is, the sector of space that falls into the frame. The shorter the focal length, the larger the viewing angle of the lens.

Depending on the viewing angle, lenses are divided into wide-angle, normal and telephoto lenses.

Wide angle A lens is considered to have an angle of view greater than that of the human eye. The focal length of wide-angle lenses is 35 millimeters or less.

The image obtained by such a lens has a rather pronounced perspective and background objects seem smaller than we are used to seeing them, but the viewing angle of such a lens allows you to shoot in tight spaces without any problems. Here are examples of photos taken with a 16mm ultra-wide-angle lens.

We can see how wide of a viewing angle this lens has, but it comes at the cost of significant perspective distortion - especially noticeable in the corners of the image. Here's another photo taken with a 16mm lens:

The same thing - the huge angle of view made it possible to fit a huge amphitheater into the frame. A pronounced perspective effect is also noticeable - small objects in the foreground seem huge, and large objects in the background seem unusually small.

Wide Angle Lenses are used in cases where one frame needs to cover a large space - mainly in landscape and interior photography. For a large angle of view you have to pay with a specific “aggressive” perspective - the lens distorts the proportions of objects in the foreground and background (see photo with the amphitheater), and also has a tendency to collapse vertical lines (see photo indoors).

Normal A lens whose angle of view is close to that of the human eye is considered. Another, more correct definition of a normal lens is a lens that has a focal length equal to the diagonal of the frame (in the case of a film frame, 43 mm). The focal length of normal lenses may vary slightly and ranges from 40 to 50 mm. Compared to a wide-angle lens, the angle of view of a normal lens may seem small, but the lens has a calmer perspective. Photos taken with such a lens are perceived most naturally, sometimes called the “effect of presence.” Here is an example photo taken with a 50mm lens.

Please note that the perspective of a normal lens is much more familiar and “calmer” than that of a wide-angle lens. The ratio of the sizes of objects in the foreground and background is familiar to the eye - this is the main advantage of a normal lens. The other side of the coin is that in order to photograph a sufficiently large object, you need to move quite far away from it. This is not very convenient and not always possible. A normal lens is best suited for shooting in open spaces, so-called “street photography”. For landscape and indoor photography, this lens may not have enough field of view to fit everything you need into the frame.

Telephoto lenses have a focal length of 60 mm or more. It’s easy to guess that the longer the focal length, the stronger the lens “zooms in”. Telephoto lenses with focal lengths up to 135 mm are often called "portrait lenses". They provide a relatively small zoom effect, so they won’t be able to take close-up shots of distant objects, but the perspective of these lenses is optimal for portrait photography—distortion of facial proportions is minimal. Here are two examples: the first portrait was taken with a wide angle (28 mm):

The photograph shows that the proportions of the face are seriously distorted - it looks excessively convex and even the eyes seem to be looking in different directions. Conclusion - if you shoot a portrait with a wide angle, it will look more like a cartoon!

Another example is a photograph taken with a focal length of 80mm:

Now the proportions are all right! Plus, the increased focal length made it possible to “stretch” and blur the background, now it does not distract us from the main objects.

When shooting even closer-up portraits, when the face occupies most of the frame, lenses with an even larger focal length are used - up to 135 mm. A longer focal length is rarely used in a classic portrait, since due to the weak perspective the face may look too flat. On the other hand, it can smooth out some imperfections, such as a too long nose.

Long focal length lenses are used when it is not possible to get close to the subject.

Please note that the photograph does not convey the depth of the landscape well - the objects in the foreground are approximately the same size as those in the background. Because of this, the landscape does not look natural. Telephoto lenses are also used when photographing shy birds and animals, for shooting sports photo reports, when you have to shoot from the stands, and the distance to the subject can be several tens of meters.

So we decided which scenes are best to shoot at which focal lengths. For simplicity, we summarize this information in a small table.

Of course, the ranges of focal lengths are approximate - it is impossible to provide for all genres and all the author's ideas in a small tablet! In real situations, the optimal focal length may differ significantly from what is given in the table.

How to find out the focal length of a lens?

To find out the focal length of a lens, just read its markings. Let's take a common Canon lens - the “whale” one (in the picture on the left)...

The arrow in the figure marks the inscription indicating the range of focal lengths - from 18 to 55 millimeters. Similar inscriptions are on all lenses without exception. If there is only one number, then the lens has a fixed focal length and does not have zoom.

Another important point that cannot be ignored is the so-called equivalent focal length. Those focal lengths discussed in the section on viewing angle and perspective apply to film cameras, as well as digital ones, which have a matrix the size of a film frame - 36 * 24 mm. Such matrices are called “full frame” or FF (from English Full Frame - full frame). They are “inserted” mainly into professional cameras. In most amateur and semi-professional devices, the matrix size is 1.5-1.6 times smaller than the film frame. Matrices of this size are called APS-C (Advanced Photo System - Classic). What happens if, say, a lens with a focal length of 50 mm is attached, for example, to a Canon EOS 650D with an APS-C matrix? How will the picture differ from the full-frame Canon EOS 5D Mark II? Let's look at the pictures...

If the EOS 5D matrix receives the entire image formed by the lens, then only the central part of the image falls on the amateur 650D matrix; it is marked with a yellow dotted frame.

As a result, photographs taken by different devices with the same lens will differ slightly from each other.

It is easy to notice that on an APS-C matrix, a 50 mm lens seems to give a smaller viewing angle. Therefore, to get the same viewing angle as a full frame, you need to reduce the focal length. How much should it be reduced to get the same picture as the full frame? Right! The same amount as the APS-C matrix is smaller than the FF matrix, that is, 1.6 times! By the way, the coefficient 1.6 is called crop factor. The higher the crop factor, the smaller the physical size of the matrix.

50mm: 1.6 = 31.25 mm

Thus, we calculated what focal length the lens should have in order to provide the same viewing angle on an APS-C matrix as that of a 50 mm lens at full frame - approximately 31 mm. In such cases they say: a lens with a real focal length of 31 mm on a 1.6 crop has an equivalent focal length of 50 mm.

Now let’s make an addition to the table with focal lengths that was drawn above...

Now let’s look at the distance scale of the kit lens and use imaginary multi-colored markers to mark the areas of application on it, something like this:

Naturally, the picture is approximate, but it clearly helps to determine what types of shooting a kit lens is suitable for. The 18-55 mm range was not chosen lightly - it allows you to perform the most popular types of amateur photography. Of course, the possibilities of a kit lens are not limitless. They are not recommended to take close-up portraits (the closest shot, the face in the entire frame); for this, a lens with a focal length of about 85 mm is desirable (so that the equivalent focal length is 135 mm). If you try to shoot such portraits at a focal length of 55 mm, you will have to do it from too close a distance, which will make the perspective distortions of the facial proportions noticeable (of course, not as much as at a wide angle, but it will still be noticeable). Also, it is impossible to shoot distant objects with a kit lens due to the lack of focal length.

People often ask me: if you buy a “superzoom” (for example, 18-200 mm), can it take beautiful portraits? Agree, it’s a tempting idea - to buy one lens for all occasions! Alas, everything is not so simple. On the one hand, the range of focal lengths of a “superzoom” really makes it universal, but on the other hand, due to its relatively small aperture ratio, it cannot always provide a shallow depth of field, which in most cases determines the beauty of a portrait. What depth of field is, why it is needed and how to control it will be discussed in the next chapter!