The lens is the most important element of any camera. And the focal length is the most important characteristic of the lens. However, for beginner amateur photographers with this characteristic, there is complete confusion. They cannot understand: for example, a lens with a focal length of 24-70 mm on a full-matrix camera is good or bad? And 15-44 mm on a "cropped" SLR - is this normal or not enough? And 7.1-28.4 mm on the "soap box" - is it very little or is it still possible to live? Well, let's figure out what the focal length of a lens is in general and what its various 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 about what these or those values ​​of focal lengths purely practically mean. 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 how the frames made with one or another focal length differ. 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 smaller the focal length, the more is placed in the frame, and the longer the focal length, the closer the lens brings distant objects closer. Small focal lengths are used to capture all sorts of things: landscapes, architecture, large groups of people. Large focal lengths are used for shooting, for example, animals and birds, for sports shooting, when you need to catch a close-up of some spectacular shot. The focal length of 50 mm is approximately the same as the field of view of the human eye (46°). Lenses with a focal length of less than 35mm are called wide angle lenses. With their help, it is convenient to shoot nature and architecture, but it should be borne in mind that the wider the angle (the shorter the focal length), the greater the distortion caused by the laws of optics will be present in the pictures. For example, if you shoot high-rise buildings with a 24mm lens, the buildings will look tilted towards the edges of the frame on the right and left - here's an example.
Lenses with a focal length of less than 20mm are called ultra-wide angle lenses and they distort the image a lot. (There's also a separate type of fisheye lens.) Here's an example photo (from here) taken with an 8mm wide angle fisheye lens.
Lenses with a long focal length 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 "fixes") and with a variable focal length (the so-called "zooms" from the word zoom, approximate). As a rule, lenses with a fixed focal length shoot better (and cost less) than a zoom set to the same focal length. That is, for example, in the general case, a 24 mm wide-angle will give better quality than a 24-70 mm zoom set to 24 mm. (There are exceptions, but we will not get into this jungle now.) And now we have come to a very important issue. And what about such a strange range of focal lengths on 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 there (it cannot change), however, since it fits noticeably less in the frame on the crop, it turns out that the "angle of view" of the lens narrows, and accordingly, for a given matrix, the focal length will be different, as it were. It is "as if different", because if the lens has a focal length of 50 mm, physically it will remain so on any matrices. But the frames will be different. Now I will explain. Suppose we have a lens with a focal length of 50mm. It forms a round image, which, superimposed on a 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. How will a frame taken with the same lens look like? It will appear within the bounds of the blue box in the illustration. That is less. And less - 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 a camera with a full size matrix. The problem is that on the lenses of cropped cameras, it is usually the physical focal length of the lens that is indicated. And in order to understand what these numbers generally mean, you need to multiply the indicated focal length by the crop size - then you will get the focal length (zoom distance) numbers in the equivalent of a full-matrix camera (35mm matrix) and begin to 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 the matrix of this camera is 3.93. So we multiply 7.1 by 3.93 and 28.4 by 3.93 - we get a range (rounded up) of 28-112 mm in 35 mm equivalent. In general, the most common range for a digital camera. Second example. Amateur DSLR with kit lens. The lens has a range of 18-55mm. The crop factor of the matrix is ​​1.6. We multiply - we get 29-88 mm. The ranger is very so-so, but you can use it. Thus, in order to clearly imagine exactly what focal lengths are available in your camera (or in the camera that you are going to buy), you need to multiply the focal range numbers indicated on the lens by the crop factor - this way you will get data on focal lengths of 35- mm equivalent, which will be quite clear to you. It is clear that for full-length cameras with their "native" lenses, no recalculations are necessary. By the way, sometimes for the convenience of users, manufacturers write on non-replaceable camera lenses both their physical focal length and its equivalent for 35 mm - this is how, for example, the Sony RX10 camera, where the physical range is 8.8-73.3, and on the installed 2.7 crop produces an excellent range of 24-200 mm: from a good wide-angle to a very decent telephoto lens.

Focal length is usually described in millimeters (mm) and is the main lens parameter. This is not a measurement of the actual length of the lens, but a calculation of the optical distance from the point where the light rays converge to form a sharp image of the object on the digital focal plane sensor. The focal length of a lens is determined when it is focused to infinity.

Focal length tells you the angle of view, how much of the scene you can capture with it, and how big individual elements can be. The longer the focal length, the narrower the angle of view and the higher the magnification. The shorter the focal length, the wider the angle of view and the lower the magnification.

Fix against zoom

There are two types of lenses - fixed and zoom. Prime lenses have a fixed focal length, while zoom lenses have a variable focal length. The advantage of zoom lenses is their versatility. They are ideal when you are shooting a variety of subjects, landscapes and portraits and want to have one lens for everything. Using a zoom lens also reduces the chances of you having to change lenses on your camera, which saves time and limits the possibility of dust getting on the lens or sensor.

The main advantages of fixes are their size and weight, as well as the maximum aperture value. Primes tend to be more compact and lighter than zoom lenses.

Also, primes have large apertures (from f/1.4 to f/2.8), which is an advantage when shooting in low light conditions, since it increases the possibility of shooting subjects handheld without the "stirring" or out of focus caused by long exposures. Shooting with a large aperture prime lens also means you can set a shallow depth of field in portraiture and get softer or blurred backgrounds (also known as bokeh).

Wide-angle lenses are a popular choice for landscapes, interiors, large group photos, and when working in confined spaces.

Prime lenses in FX format, 50-60mm / DX format 35mm

Standard lenses are popular because they display reality close to how people see it. These lenses have minimal distortion, which allows you to show objects in a favorable light. They tend to use large apertures and absorb a lot of light, allowing you to take quick shots in low light conditions. Large apertures (f / 1.8-f / 1.4) also allow you to keep the image sharp not only in focus, but also in the background. Standard lenses are also popular when shooting portraits in low light conditions where the photographer cannot use a flash or is looking to take a photo using the available light.

Telephoto lenses in FX format 70-200mm / in DX format 55-200mm

Telephoto lenses 70-200mm are very popular for portrait and product photography, as well as nature and animal photography. They allow the photographer to get closer to the subject. When creating portraits, a telephoto lens allows the photographer to take a picture from a distance without invading the personal space of the person being photographed.

Super telephoto lenses in FX format 300 - 600mm/DX format 200-600mm

These lenses have good range for sports and wildlife photography where the photographer cannot get close to the subject.

Macro lenses: FX formats 60mm, 105mm, and 200mm/DX format 85mm

When shooting close-ups, a certain range of lenses is used, which allows reproduction up to 1:1. These lenses allow the photographer to get very close to the subject and reproduce it at a 1:1 life-size ratio on the lens sensor. These lenses are popular for shooting objects such as flowers, insects and small objects.

Choosing a lens for a photographer is even more important than choosing a camera. In this review you will find a description of the focal lengths from 14mm to 300mm. Each focal length has its own specifics, this must be taken into account when choosing a lens. I think you need to start with a whale lens. You can even zoom like 18-135, and only then approach the choice of more specialized optics. It is an individual and creative process.

The optimal focal length depends on:

• filming genre
• filming locations
• work specifics
• creative vision of each photographer

With all this, you can decide only if you already have some experience in photography. Below I will share my observations. All information is related to working with . If you have a crop sensor camera, multiply the focal length by one and a half.

fish eye

The shot from above was taken with a lens. This lens gives full frame coverage on a crop camera and a black-edged circle on a . The viewing angle is 180 degrees diagonally. Frames, competently made on fisheye, look bewitching. The peculiarity of this focal length ( available from 4mm to 15mm) in that it has a very narrow scope. Fisheye is a lens with the widest possible angle of view, but without distortion correction. The end result is rounded lines that should be straight and a very specific perspective. Such a lens is taken with you for the sake of several bright shots. It is difficult to use them for a long time.

14mm

The focal length lens is also very specific. This concerns the geometry of the resulting image. The slightest incorrect tilt of the camera causes severe distortion. This is especially felt when. In nature, the horizon easily collapses. The angle of view is very wide - you need to understand if you need it. It has advantages: you can, for example, remove the entire interior of the car from the inside; in any cramped room you will not have problems with the viewing angle; in nature, you can make interesting panoramas with a three-dimensional foreground. You can shoot portraits with such a focal length only very carefully and in full growth. In general, shooting people on a lens with such a focal length should be extremely thoughtful. This, however, applies to any filming - here, before taking a picture, you need to think. The 14mm lens is not an everyday tool.

24mm

24mm- a fairly wide angle. When working with a wide angle lens, you always need to think about what should and should not be in the frame. This focal length is easier to work with. It does not distort space as much and is more in line with conventional perception. At 24mm it is very comfortable to shoot indoors. Taking over the whole room will not be a problem. At the same time, geometric distortions are much less pronounced. This is a convenient focal length, you can travel with it (which I would not advise you to do with only 14mm), shoot a report inside small rooms, and take landscape shots. For portraits, the 24mm lens, again, is of little use.

Publication date: 19.01.2015

How does the size of the camera's matrix affect the angle of view of the lens?

This is the third part of the lesson about camera lenses. In the first and second parts, we got acquainted with the device and the main characteristics of the 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 field of view.

The longer the focal length of the lens, the narrower its field of view.

When a person uses his own camera, he eventually gets used to the fact that at certain focal lengths, his lens gives one or another viewing angle: “brings” the scene being shot stronger or weaker. Will these ratios between focal length and viewing angle remain the same or change if the camera is changed? Today we will find out. Often, when discussing pictures, photographers say: “this picture was taken at such and such a focal length,” thereby characterizing the angle of view at which the image was taken. Even under photo examples in our articles, the focal length of the lens on 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 to take a photo with your camera?

We have to figure out how the angle of view 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

Earlier, in the film era, 35 mm film was the most widely used - an ordinary photographic film familiar to every person. It was used everywhere, from the simplest compact cameras (probably everyone had a film “soap box”), ending with 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 working with 35mm film, a lens with a focal length of 50mm had a 45° angle of view. Recall that modern full-frame digital cameras also use a sensor that is equal in size to a film frame - 24x36 mm.

Lens viewing angle and sensor size

Today the situation has changed. Matrices 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's 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” sensor, the same lens will give a field of view of just 15°. The smaller the matrix in the camera, the stronger the lens with the same focal length will “zoom in”. The same lens, when mounted on different cameras, will give a completely different picture. This must be taken into account when choosing optics.

Since sensors of completely different sizes are installed in various cameras today, it is easy to get confused with what angle of view a lens with a particular focal length will give on a particular camera.

Photographers of the old school, 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 (EFF)

This characteristic is not needed for beginners, those who bought their first camera - the numbers of the equivalent focal length will not tell him anything. But for experienced photographers who are accustomed to film photography, this feature will be 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 right optics for it, to find out how their old lenses will work on the new camera.

The equivalent focal length lets you know what focal length a lens with the same angle of view 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 specifications of a lens that is not designed for a full-frame camera, you can often find the item “equivalent focal length” or “35mm equivalent focal length”. This item is needed so that the photographer can figure out what angle of view this lens will give. For example, for a 50mm lens mounted on an APS-C sensor camera, the equivalent focal length would be 75mm. The tiny focal length of 4.3mm used in a compact camera lens matches the angle of view of a 24mm lens at full frame.

How to calculate the most equivalent focal length? To do this, you need to know the crop factor. This is a conditional factor that reflects the change in the angle of view of the lens when it is used with smaller sensors. This multiplier is derived when comparing the diagonals of digital camera matrices with a 24x36 mm film frame. The word "crop factor" comes from the English words crop - "cut off" 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 the APS-C matrix will be 1.5. But the diagonal of the Nikon CX format matrix is ​​\u200b\u200bless than full-frame by 2.7 times. 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 an APS-C sensor camera. 35x1.5=50mm. So, the equivalent focal length of such a lens would be 50mm. That is, on an amateur DSLR, a 35mm lens will behave in the same way as a classic “fifty kopeck” on a full frame.

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

Sensor sizes and crop factor for Nikon photography

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

Full frame matrices(Nikon FX). They have a physical size of 36x24 mm, that is, they are equal in size to a frame from a 35 mm film. Most modern lenses are designed for such cameras. And on them they can reveal their full potential. Among modern Nikon devices, full-frame matrices are equipped with: 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, 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 it is much cheaper. Such matrices are sometimes called "cropped" (cropped). Almost all manufacturers of digital SLR cameras use this sensor size. Among modern Nikon devices, APS-C matrices have cameras Nikon D3300, Nikon D5300, Nikon D5500, Nikon D7100. You can still use full-frame optics with them, however, all lenses will “zoom in” much stronger, which is not always convenient, because some lenses are designed for a strictly specific type of shooting and the loss of the desired 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; portrait full-frame lenses on the “crop” start to get too close, and it becomes difficult to shoot on them, you have to move very far. For example, by installing 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) get uncomfortable 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 these lenses are designed to be used on a smaller sensor, they themselves become smaller and cheaper than their full-frame counterparts.

For the same reason, they will not be able to work correctly on full-frame mothers. What happens if you put a cropped lens on a full frame camera? Unlike Canon cameras, Nikon has such an opportunity. In this case, you will get a very strong darkening at the edges of the frame. By the way, modern full-frame Nikon cameras can recognize “cropped” optics if installed, 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.

Camera lenses consist of several lenses that form an image on the matrix. And considering the optical characteristics of the lens, replace the lens group with one for ease of understanding. By physical properties the focal length of a lens is the distance from the optical center of the lens group to the matrix. This distance is measured in millimeters and written on the lens.

For photographers, it is much more important to understand the dependence of the resulting image on the focal length.

According to the ratio of the focal length (FR) and the diagonal of the frame, lenses can be divided into three large groups:

1. If the FR is approximately equal to the diagonal of the frame (matrix), then such lenses are called normal.
2. If the FR is less than the diagonal of the frame, then the lens short throw.
3. If the FR is larger than the diagonal of the frame, then the lens is telephoto.

In photography, all calculations are made using the frame size of 35 mm film, which is used in film cameras. So its diagonal is 43 millimeters. So also in physics it is believed that for the angle of view of the human eye, a focal length of 50 millimeters is considered normal. Therefore, everywhere in photographic technology, a distance of 50 millimeters is considered a normal focal length.

Now you can divide the lenses into types by focal length.

Focal length	Lens Type	Shooting targets	Viewing angle
4 - 16 mm	fish eye	landscape, art, landscapes	180°
10 - 24 mm	ultra wide-angle	interior, landscape, deliberate distortion of proportions	84 - 109°
24 - 35 mm	wide-angle	landscape, architecture, street photography	62 - 84°
50 mm (35 - 65)	standard	landscape, portrait	46° (32 - 62)
65 - 300 mm	telephoto lens	portrait, sport, nature	8 - 32°
300 - 600 or more mm	super telephoto	animals and sports from afar	4 - 8°

In this table, you can see the dependence of the viewing angle on the focal length. It turns out that the smaller the FR, the greater the viewing angle. Shooting with a lens with a wide angle of view changes the perspective of the image, this is expressed in a change in the proportions of the subjects being photographed.

With normal (standard) lenses, with a focal length of about 50 mm, the pictures are the most natural in perception. Best suited for street photography (street photo).

Lenses with FR from 50 mm to 130 mm can serve as portrait lenses. The most suitable is 80 mm FR for portraits.

Variable focal length

There are lenses with a fixed or fixed focal length and with a variable one. On lenses with variable FR, a pair of numbers is indicated - long and short focus. By dividing one value by another, we get the zoom ratio, which is indicated on the camera.

The zoom ratio does not mean at all how many times the object will increase, the zoom only shows that the lens has a variable focal length. Today there are 80x zoom lenses. The disadvantage of such lenses is the decrease in aperture ratio. To achieve a large aperture, lenses with a fixed focal length are used.

Focal length and crop factor

All of the above numerical values ​​are valid for 35 mm film and for digital matrices, the dimensions of which correspond to the frame of 35 mm film. Such matrices are called Full Frame.

But matrices come in different sizes, and to reduce the cost of cameras, they are made much smaller than Full Frame. Such matrices are called cropped, from the word crop (crop).

This is how the crop factor appeared, which shows how many times the matrix is ​​​​smaller than the film frame and this coefficient is equal to the ratio of the diagonal of the full frame to the diagonal of the matrix.

A Full Frame matrix will have a crop factor of 1.

And now, if the lens is not used with a full frame, but with such a cropped matrix, then the viewing angle changes. This corresponds to a virtual increase in focal length. Although the real FR remains unchanged, because this is a characteristic of the lens. The crop factor is a reference factor and does not change the actual parameters of the lens.

For example, using a cropped sensor with a crop factor of 1.6, we get that a lens with a 50 mm focal length with this sensor will already have a virtual focal length of 50x1.6 = 80 mm. Such a focal length is called equivalent (EGF). That is, we take the focal length indicated on the lens and multiply by the crop factor.

The figure above shows that by using a smaller matrix, we get a smaller viewing angle, and this changes the boundaries of the image (reduces the boundaries). It seems that we enlarged the object by changing the focal length of the lens, but the FR remained the same.

The equivalent focal length is already more a characteristic of the lens + matrix bundle.

Choosing a lens with a specific focal length depends on your creative preferences, frame composition.