Why do you need a focal length of 35 mm. Focal length and perspective. Effect of focal length on blur

The focal length of a lens is, one might say, its most important characteristic. Modern optical systems contain a considerable number of lenses, fixed lenses have fewer, and zoom lenses more.

Understanding the terminology

To put it as simply as possible, then focal length The lens is the distance from the lens to the focal point on the film or sensor. In this case, the depicted object should be at a sufficiently large distance. The human eye is designed in much the same way as a lens. We see everything around at an angle of 45 degrees. A normal or stock lens sees everything from the same angle. If the focal length of the lens is equal in value to the diagonal of the frame, then we are talking about a regular representative. However, it can be more or less. So, the longer the focal length, the smaller the angle, and vice versa.

About standards and types

A focus rate of 35 millimeters has always been considered the standard. However, modern digital technology can be supplied with a matrix that is equal in size to the film frame, that is, 24 * 36 mm. These cameras are considered to be full-matrix. Their optics work in exactly the same way as those of film. The conversation is about this standard. In accordance with the Pythagorean theorem, the frame diagonal will be 43.3 mm. In this regard, for a standard lens, the focal length should be 45 mm. The closest in value is the lens for which this parameter is 50 mm. It is much more interesting if the focus value is less or more than this. If the focal length of the lens is 8-20 mm, then it will be called ultra-wide-angle, allowing full-length shooting in a tight room, with a value of 21-35 mm we are talking about wide-angle models, and 50 - about standard ones. The 70-85mm focus is used for portrait subjects. For telephoto lenses, the focal length ranges from 100 to 1000-1200 mm. Some firms produce models for which this value is 2000 mm. With their help, you can take pictures of very, very distant objects.

Tips for choosing

If you are faced with the question of choosing a lens depending on its focal length, then it is worth considering a number of points. You must decide how wide your viewing angle is. Sometimes 18 mm is enough. It is worth starting with a wide angle, since there is always a need for it, but it is important to determine how wide it should be so that you do not have to buy another lens later. If you do not need more than 18 mm, then the task is greatly simplified, since at the moment there are many lenses with just such an initial focus. It is possible that later on you will need an even wider-angle solution, which is when you can turn your attention to variable focal length lenses. It should be said that there are a lot of starting values. When choosing the best option, you should look at the reviews about a particular lens, as well as photos that can be obtained with its help. It is most correct if you have two lenses in your arsenal, one of which overlaps the other in focus.

So, now you know not only what is the focal length of the lens, but also many nuances to which you should pay attention when choosing it.

A camera lens is a lens system and one of its main characteristics is the focal length.

In order to understand the question of what is the focal length of the lens and what it affects, you will have to remember a little physics.

So, the rays of light, reflected from objects, pass through the objective lens (lenses are installed not one, but several lenses, but for now we will not complicate things). Since the subject is usually located at a considerable distance from the lens, the reflected light beams can be considered parallel to each other.

When passing through the lens, the rays are refracted and, at some distance from it, they are "collected" into a point. This point is called the focus, and the distance from the focus to the lens is called the focal length. The plane that is perpendicular to the main optical axis of the lens and passes through the focus is called the focal plane. An image is formed on it.

The figure shows an ideal situation, but nevertheless, we will proceed from it.
In fact, the whole principle of "transferring" a real image to the camera matrix can be represented like this:

We can say that the focal length of a lens is the distance from its optical center to the camera's matrix, that is, to the plane onto which the image is projected.

This we examined the physical meaning of the concept of "focal length", but if you do not go into the details of optics and generally forget about physics, then the focal length determines how much the lens will be able to "bring closer" the subject. Therefore, you can remember one simple rule:

the longer the focal length of the lens, the visually closer the subject will be in the photograph

Focal length is measured in millimeters and is usually indicated on the camera lens.

Various angles of field coverage

The field of the frame covered by the lens can be expressed as the angle of coverage of the field of the frame. Typically, for 35 mm film, focal lengths from 40 to 60 mm generally correspond to the picture that the naked eye perceives in perspective.

Lenses with focal lengths shorter than this standard focal range are called "wide-angle", and lenses with focal lengths longer than the standard range are called "telescopic" lenses. The shorter the focal length, the wider the angle of coverage of the field of the frame becomes (hence the name "wide-angle"), and the longer the focal length, the narrower the angle of coverage of the field of the frame (for "telescopic" lenses).

* The ratio between focal length and field of view is always constant, regardless of the lens focal lengths used. However, in exceptional cases, due to different design principles and distances from the camera to the subject, the angles of the field of view may differ.

Perspective

The lens displays close objects as larger and distant objects as smaller. When using a wide-angle lens, the focal length is shorter and this effect is enhanced, that is, close objects are reproduced with emphasis large, and distant objects very small (enhanced perspective).

When working with telescopic lenses, the opposite effect is observed, that is, the distant parts of the plot are reproduced somewhat more, and the close parts are somewhat smaller than it is perceived by the naked human eye (flattened perspective).

Depth of field

When focusing the lens from a certain distance, there are areas in front of and behind the subject, which also appear sharply. This range is referred to as the sharpness range. If it is small, they speak of "shallow depth of field", and if it is large, they speak of "great depth of field".
The range of the sharply displayed area becomes smaller with decreasing the set aperture number (i.e., when the aperture opens!), And vice versa. In addition, with the same distance setting, the depth of the sharply displayed space is less, the greater the focal length of the lens.

Comparison of a lens with a variable focal length and a lens with a fixed focal length

Varifocal lens is versatile

A lens with a variable (adjustable) focal length allows you to smoothly adjust the focal length without changing focus. In this case, the capabilities of a whole group of lenses with a constant focal length are combined in one single lens.

Standard focal range	Standard lens (28-80mm), Telescopic focal length range (80-210 mm).
Extended focal length range	Ultra wide angle range (11-18mm, 17-35mm, 19-35mm), High-end telescopic lens with low dispersion (70-300mm LD), Ultra telescopic lens (200-500mm).
Megazoom range	High-end wide-angle lenses (24-135mm), Standard lenses with adjustable focal length (28-105 mm), Megazoom type lenses (18-200 mm, 28-200 mm, 28-300 mm).
Fast ZOOM Lenses	Wide-angle ZOOM lenses (17-35mm f / 2.8-4), Standard ZOOM lenses (28-75mm f / 2.8).

Lenses with constant focal length and maximum image quality

A lens with a constant focal length can be optimally used in its special area, which provides a combination of compactness with extraordinary high image quality. Tamron offers a range of fixed focal length lenses that successfully take advantage of the technologies originally developed for variable focal length lenses.

Ultra wide angle lens (AF 14mm),
Macro lens (90mm f / 2.8 1: 1, 180mm f / 3.5 1: 1),
Fast telescopic lens (300mm F / 2.8),
Mirror lens (500mm f / 8) (supplied as manual focus lens only).

Macro (close-up)

Dedicated macro lens

A macro lens (MACRO) is optimized for photographing small objects as large as possible. MACRO lenses correct display errors that are more apparent when shooting at close distances.

Display scale

The display scale is expressed as the ratio of the original size of the displayed object (1) to the size of its reproduction on film (1 / X) in numbers: 1: X.
The higher the X-number, the less part of the original object appears on the film. A coin displayed on film with the same size as the actual (life size) is reproduced at a 1: 1 display scale. A display scale of 1: 2 means that the film only displays at half its true size.

Macro ZOOM Lens

As mentioned above, macro photography is a method of displaying small objects in photography. Macro photography is possible not only with special lenses, but also with telescopic lenses with variable focal length (ZOOM lenses), provided that the telescopic lens has the appropriate setting. Tamron lenses, designated "MACRO" on the barrel, are capable of display ratios of at least 1: 4.

Solar hood

With the exception of a few models, most Tamron lenses come with a sun hood (also incorrectly referred to as the "Backlight Hood"). These Tamron solar hoods are an essential component of optical rendering to suppress unwanted stray light and loss of contrast. This applies not only to fixed focal length lenses, but (to a greater extent) to variable focal length lenses, where the shortest focal length serves as the starting point for optical image rendering.

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The lens is an essential element of any camera. And the focal length is the most important characteristic of the lens. However, budding amateur photographers with this characteristic are in 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? Is 15-44 mm on a "cropped" SLR normal or not enough? And 7.1-28.4 mm on the "soap dish" - is it very little or is it still possible to live? Well, let's figure out what the focal length of a lens is and what its different values \u200b\u200bmean. A lens is a system of multiple lenses. The image of the captured object enters the lens, refracts there and converges to one point at a certain distance from the rear of the lens. This point is called focus(focus point), and the distance from focus to lens (lens system) is called focal length.

Now about what purely practically mean these or those values \u200b\u200bof focal lengths. Initially, let us agree that we are now talking about a lens designed for shooting with a full-matrix camera (in this article we talked about what a "full matrix" is). Let's take a purely practical look at the difference between shots taken with one or another focal length. We shoot from one point and change the 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 it fits into the frame, and the longer the focal length, the closer the lens brings distant objects closer. Small focal lengths are used for all kinds of photography: 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 capture some spectacular close-up shot. A focal length of 50 mm is roughly equivalent to the viewing angle of the human eye (46 °). Lenses with focal lengths 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 (shorter the focal length), the greater the distortions caused by the laws of optics will be present in the pictures. 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, the buildings on the right and left will look tilted - for example.
Lenses with focal lengths less than 20mm are called ultra wide-angle lenses and they distort the image very much. (There's also a separate kind of fisheye lens.) Here's an example of a photo (from here) taken with a wide angle. " fish eye"with a focal length of 8 mm.
Lenses with long focal lengths are called "telephoto lenses", and those with very long focal lengths are called "telephoto lenses". In general, the classification there is approximately the following: 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, zoom in). In general, fixed focal length lenses perform better (and cost less) than a zoom set at the same focal length. That is, for example, in general, a 24mm wide-angle will give better quality than a 24-70mm zoom set at 24mm. (There are exceptions, but we will not go into this jungle now.) And now we come to a very important question. What is this strange focal length range of my Fujifilm X20, you might ask? It says 7.1-28.4 mm. It's 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 much less is placed in the frame on the crop, it turns out that the "angle of view" of the lens narrows, and accordingly, for this 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 so on any matrices. But the frames will be different. Let me explain now. Let's say we have a lens with a focal length of 50mm. It forms a circular image, which, when 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 2. How will a frame taken with the same lens look like? It will appear within the blue rectangle in the illustration. That is, less. And smaller - 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 multiplied by the crop factor) on a camera with full-size matrix. The problem is that the lenses of cropped cameras usually indicate the physical focal length of the lens. And in order to understand what these numbers mean in general, you need to multiply the indicated 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 begin to understand what range of focal lengths is present in this the camera. Example. Fujifilm camera Finepix X20, zoom range 7.1-28.4mm. The crop factor of the matrix of this camera is 3.93. So multiplying 7.1 by 3.93 and 28.4 by 3.93 - we get the range (rounding up) 28-112 mm in 35 mm equivalent. In general, the most common range for a digital camera. Second example. An amateur SLR with a whale lens. The lens shows a range of 18-55mm. The crop factor of the matrix is \u200b\u200b1.6. We multiply - we get 29-88 mm. The range is very so-so, but you can use it. Thus, in order to clearly imagine which 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 will give you data on focal lengths of 35 mm equivalent, which will be quite clear to you. It is clear that no recalculations are needed for full-frame cameras with their "native" lenses. By the way, sometimes for the convenience of users, manufacturers write on non-interchangeable camera lenses both their physical focal length, and its equivalent for 35 mm - this is how, for example, in sony cameras RX10, where the physical range is 8.8-73.3, and with a crop of 2.7 it is an excellent range of 24-200mm: from a good wide-angle to a very decent telephoto lens.

Turitsyn Andrey

Focal length

Focal length is the distance from the optical center of the lens to the focal point (in mm), i.e. to the film (matrix), where a sharp image of the object is formed. For example, a focal length of 50, or 120 mm. And what is the difference? The difference lies in the choice of frame boundaries. Let's see what pictures can be taken from the same point of view: the photographer does not move, but changes the focal length of the lens (or changes the lenses themselves on the camera).

focal length 24 mm, 30 mm, 50 mm, 120 mm, 180 mm, 300 mm

the shooting was carried out from a distance of 15-17 meters (from the window of the 4th floor of an ordinary five-story building), 2 lenses were used: a wide-angle zoom from Pentax, and a long-focus Soviet lens Granit-11m

In general, everything is not difficult: the more we increase the focal length, the more we zoom in on the subject of photography (or, conversely, reduce it). It's even simpler: what is more than 50 mm, we increase, everything less than 50 - we reduce. And, quite simply: a focal length of 100 mm is a 2x magnification, 180 mm is a 3.6x magnification. It couldn't be easier. But why was 50 mm chosen as the starting point? It is generally accepted that such a focal length corresponds to the angle of view of the human eye (in fact, the peripheral vision of the eye covers a much larger angle). They also believe that a standard lens has a focal length of 50 mm, since this is close to the diagonal of a film frame (43 mm). Don't look for complications in this. Sometimes they are created only in order to then successfully overcome :)

How to find out the focal length of a lens

This has already been discussed in the article "lenses", we repeat for those who came here from other pages. How do I know the focal length? Very simple. The focal length is indicated on the lens barrel, next to its aperture. In the photo on the left we see the old Soviet Helios 44k-4, which has a focal length of 58 mm and aperture f2 (designated 1: 2). I indicated the focal length in the photograph with a yellow arrow.

What else can you tell about the lens by looking at its designations? Little.

This Helios model has a "K" bayonet mount (will fit under a Pentax SLR without any adapters), multilayer coating, a constant focal length of 58 mm, aperture f2, a mounting thread for light filters - М52x0.75, the lens itself was produced for Zenit cameras with a "K mount." "at the Krasnogorsk Mechanical Plant, the latter is indicated by the prism icon with a refracted beam ... You can, of course, tell much more about this optics than its designations say - but this is beyond the scope of the article about the focal length ...

What is zoom

I already mentioned in the article "How to choose a camera" that stores often mention this characteristic. Actually, what is zoom? Zoom is a lens with a variable focal length, it is also a "zoom", it is a "zoom lens" - there are many names, but the meaning is the same. Or more precisely, complete absence such :) For example, we have a typical focal length of a lens of 28-55 mm. Divide 55 by 28 and get approximately 2. This means 2x zoom :) This figure is absolutely useless, because, for example, a 100-200mm variable focal lens also has 2x zoom, but these are completely different lenses , with different angles and for completely different tasks. In this regard, only the focal length is a useful characteristic, therefore, let us return to the study of it, and forget the marketing word zoom, or we will use it not for meaningless calculations, but only to denote a zoom lens. Therefore:

Zoom is a lens that has a variable focal length. And nothing more!

The zoom, of course, is convenient, but in the red at the long end of the zoom, the aperture almost always drops (especially for cheap optics). For example, the compact lens says 5.8-24 / 2.8-4.8. The last two digits indicate the lens aperture, at the short end it will be 2.8, at the long end, respectively, less - 4.8. Those. with increasing focal length, the aperture will drop! Therefore, one small tip: don't chase the huge zoom! There are digital compacts (we read - a small matrix!), With 20-30x (and even more) zoom. And here, when shooting at the long end of the zoom, the lens aperture closes sharply, and as a result, less light comes in. This means that fast shutter speeds will become unavailable, and shooting on long exposures (without using a tripod) will lead to shake and blurry shots; either automation (or you) in response increases the photosensitivity of the matrix, i.e. increases the signal on it, and the small camera matrix makes noise, but what is the result? Disgusting pictures. Therefore, choose 3-4x zoom, otherwise, if you are not going to work with a tripod, it will be a waste of money!

The zoom is not a prime lens, it's a prime focus, it's a discrete lens ... I haven't missed anything? Yes! It is also a fixed focal length lens :) You have already seen the fix in the picture of Helios above. Once all lenses were fixed, the first zooms appeared in the 60s of the last century, for example, the Rubin 1ts lens, focal length 37-80, aperture ratio 2.8, was a standard lens for the Zenit-6 camera.

The zooms of that time had an interesting characteristic feature - they did not lose focus when changing the focal length! Modern lenses are deprived of this: alas, you need to focus on sharpness every time after zooming ... And this muck was done in the name of reducing the cost of production. Autofocus, of course, helps, but if manual focusing is necessary (and it is sometimes necessary!), Then one can only envy the miracles of the old mechanics (and most importantly - the attitude to business).

Focal length in 35 mm equivalent (EGF)

There are two focal lengths - real, and equivalent to 35 mm format cameras. The real is indicated on the lens, the equivalent does not exist in nature, it is calculated. Why such difficulties and what is it for? The fact is that film cameras (35 mm format) have the same frame size: 24 x 36 mm, and therefore it was easy to compare their lenses. If one camera had a lens focal length of 50 mm (standard fifty-kopeck piece), then a lens of, say, 28 mm was called a wide-angle lens, 70-100 mm - a portrait lens, and over 100-150 mm - a telephoto (or long-focus lens). This division was arbitrary, but it was understandable and suited everyone - some had a wider angle of view, while others had a narrower one. Actually, we are talking about the angle of view of the lens, just "bad" photographers confuse the beginner with creepy terms: "focal length", "equivalent focal length", "EGF", "Crop factor of the matrix", just "crop", and other rubbish, which has only a side relation to the angle of view of photography, and therefore to the composition of the frame :) In general, in the era of 35 mm photographic film it was easier to compare lenses and take photography, and not nonsense :)

Photographers are generally somewhat strange people. If you ask them - in what units the aperture is measured, then instead of an unambiguous answer, you can hear a rather lengthy speech about the ratio of the focal length to the diameter of the effective aperture of the lens. They measure angles not in degrees, but in millimeters, the angle itself is called the focal length, and the photographic film is called 35 mm (and even 135 mm), although the frame size is ... 36x24. Where the hell did this 35mm come from? It's simple, let's not invent new standards, but rather try to understand the old ones.

What is 35mm format? 35 mm is the width of the foil with the perforated part.

Sometimes 35 mm film is designated as type 135. Index 1 before the number 35 was introduced by Kodak in 1934 to indicate perforation (before that the film was not perforated). Later, other formats were offered, but they did not take root: 35 mm photographic film ousted everyone. And only a separate niche is occupied by cameras of medium and large formats.

However, with the advent of digital cameras, this has changed. If digital cameras had the same matrix size - 24 x 36 mm, there would be no difficulties in comparing lenses. But this size from digital cameras have only very expensive professional grade DSLRs. Amateur DSLRs have a matrix size 1.5-2 times smaller than "full-size" ones, and digital compacts are even smaller than amateur ones. Such cameras are considered not 35mm format and are designated APS-C, 4/3 and others depending on the size of the sensor. Naturally, the smaller the matrix, the smaller the angle of view of the lens. Therefore, it became impossible to compare the same focal length if the cameras have different matrix sizes. To avoid confusion, it was decided to introduce the term "equivalent focal length" (EFD), i.e. focal length for 35 mm format cameras - to compare with 35 mm wide film with 36x24 mm frame size. On the lens, as a rule, the real focal length is indicated, and in the user's manual you can find out which EGF it corresponds to. Sometimes you can find out in short description cameras in the store.

The focal length of the same lens does not change when attached to a camera with a smaller sensor - the angle of view changes. But, if you want, the focal length of the entire system has changed (matrix + lens).

EGF is used only for comparing camera lenses with different crop factors - comparison by angle of view. The terminology is as follows: if a lens with a focal length of 50 mm is installed on a matrix 1.5 times smaller than a full-frame one, then they say that the EGF has become 75 mm - the angle of view becomes the same as if the focal length were 75 mm. It turns out this is what. Yes, the focal length of the entire system has changed (for the lenses themselves - no!), But the distortions have not changed within this lens, since they were "sharpened" at 50mm, not 75.

On a smaller sensor - at the same focal length - the frame will be cropped and the angle of view is smaller

If the size of the matrix is \u200b\u200bknown, the equivalent is easy to calculate. How many times the camera's matrix is \u200b\u200bsmaller than a film frame, then the real focal length must be multiplied by so much to find out the equivalent. This difference (or rather the multiplier) is usually called the crop factor of the matrix. For example, nikon DSLRs have a matrix size of 23.7 x 15.6. If the wide side of the film frame (i.e. 36 mm) is divided by 23.7, then the crop factor (here by crop I mean the aspect ratio) will be about 1.5. You can also divide the other side: 24 by 15.6, there will be the same crop. This means that the actual focal length indicated on the lens must be multiplied by 1.5 to get the equivalent. For example, a kit lens (from the English KIT - kit) for Nikon has a real focal length of 18-55 mm. We multiply 18 by one and a half, and 55 by one and a half, as a result we get 27-82 in 35 mm equivalent. And what does it mean? Rejoice, this is a versatile lens - there is a wide angle for landscapes, and at the long one you can even shoot portraits at the very least! The only pity is that the whale's aperture is weak, but that's a completely different conversation.

Equivalent focal length is used to compare camera lenses with different crop factors.

Those. when the matrix of such cameras is not the same size.

Table of crop factors for different camera formats

The Russian word "multiplier" has long been replaced by the expression "Crop factor", apparently to give your speech outlandish overseas shades, like, don't think that I'm from Russia, I'm like from the states :-) Let's see the multiplier (or crop) for typical photosensitive sizes camera elements:

Company	Designation	Size mm	Crop
FED	film 35 mm	36 mm x 24 mm	1
Nikon	"APS-C"	23.7 x 15.6	1.5
Pentax	"APS-C"	23.5 x 15.7	1.5
Sony	"APS-C"	23.6 x 15.8	1.5
Canon	"APS-C"	22.3 x 14.9	1.6
Olympus	4/3	18.3 x 13.0	2
compact	1/1.8	7.2 x 5.3	4.8
compact	1/2.5	5.8 x 4.3	6.2
compact	1/3.2	4.5 x 3.4	8

As for compacts, they have matrices 4-8 times smaller than the size of a film frame! For example, a typical 1 / 2.5 "" die is 5.8 mm wide on the wide side. 6.2 times less than 36 mm of the side of the film. The lens of such a camera with a focal length of, for example, 5.6 - 17.7 mm, will correspond to 35 - 110 mm EGF. Let's take an SLR camera with a 1.5 crop and a lens marked with a focal length of 16 - 45 mm. After multiplying by 1.5 we get the equivalent focal length - it will be 24 - 67 mm. Now you can compare the lenses of these cameras - this compact has a longer lens, and a DSLR with a wider angle. Whatever one may say, but all sizes will be compared with 35 mm film for a long time!

Focal length and lens types

More precisely, the equivalent focal length, types of photography and angle of view of lenses for 35 mm cameras. Here we can clearly see how meaningless the word zoom, or rather the zoom ratio :) Focal length rules!

focal distance	lens	photography goals	vision angle
4 - 16 mm	fish eye	landscape, art, special physical landscapes	180 ° and more
10 - 24 mm	in excess of- wide-angle	interior, landscape, intent distortion of proportions	84 - 109 °
24 - 35 mm	wide-angle	landscape, architecture, street photography	62 - 84 °
50 mm (35 - 65)	standard	landscape, portrait, macro * and whatever you like!	46 ° (32 - 62)
65 - 300 mm	telephoto lens	portrait, sport nature, macro *	8 - 32 °
300 - 600 and more mm	super- telephoto lens	animals and sports from afar	4 - 8 °

* Macro photography depends more on the special properties of the lens than on the focal length.

For example, it is good to shoot a landscape with a wide-angle: with such optics, the depth of field is higher, and at a wide angle, it will fit more). A wide angle is important in a landscape, in an apartment, in architecture, in a city, in any limited and unlimited space, and wherever it is necessary to emphasize the expressiveness or dynamics of the plot. And with a telephoto lens it is convenient to enlarge, i.e. zoom in on a hard-to-reach subject. For example, the face of a lion in the wild and in the whole frame :) The wide-angle has a focal length of less than 35 mm, standard 35-65 mm, telephoto lens - from 65 to 300 mm and even higher.

A station wagon can have them all in one bottle, for example, 24-200, 35-105, 28-116 mm, etc., which is its main advantage. The disadvantage of all station wagons is that they are inferior to a specialized one (for example, a telephoto lens), as a rule, in terms of aperture ratio, or maximum focal length, or in price (with the same aperture ratio, the price will be higher), or in quality.

A simple (nowhere easier!) Picture on the left will help you to understand all of the above about the angle of view of various lenses. We clearly see how the focal length changes the angle of coverage of the frame, i.e. the scene being filmed, or the plot. This division is, of course, very arbitrary. Landscapes are also shot with a long telephoto lens, and everything, even up to portraits, is taken with a wide-angle telephoto lens.

It is clear that the choice of lens always depends on the tasks, creative preferences and even the mood of the photographer. Beginners can take a large zoom with a coverage of 28-200 mm (or 24-1000 mm, there is even one!), And end up with a huge selection of focal lengths, here you have a wide-angle + standard + telephoto + very large telephoto, and all the happiness in one bottle.

Indeed, why bother with a selection of kilograms of additional optics! However, the disadvantage of this choice is a small aperture ratio (especially at the maximum focal length), and optical distortion (aberration), alas, all large zooms have similar disadvantages.

Focal length and aberration

The greater the difference between a wide angle and a long one, the stronger the optical distortion of all kinds, called aberrations. Engineers reduce them to a minimum by adding low-dispersion and aspherical lenses to the optical scheme, but then the weight and price of the lens will be much higher. Moreover, the aberrations are not eliminated until the end, they are simply made less noticeable, as much as possible. Therefore, a universal lens, solving one problem, generates new ones :)

The best in this regard would be a prime lens - a lens with a fixed focal length (it has only one). Distortion in this is easier to remove than in zoom. In addition, fixes are distinguished by a higher aperture ratio, smaller dimensions, and the most worthy price / light ratio. And, nevertheless, the coverage of several focal lengths at once (which is what the station wagon does) attracts many ...

There are three main groups of aberrations: distortion (geometric distortion), chromatic aberration (color distortion), and, finally, diffraction (loss of sharpness at strongly clamped apertures). The most common example for a wide angle lens is distortion. The wider the angle and scope of the zoom, the more so-called. barrel distortion (if not corrected with additional lenses). To get a clearer idea of \u200b\u200bthis thing, see the picture.

A very curved photograph is, of course, inherent in inexpensive lenses or fisheye optics, but not crooked hands. Although ... how to say, the cases are different. For example, crooked hands are not able to correct distortion either in Photoshop or in any other graphics editor!

Below is an example of geometric distortion (barrel distortion) of the very expensive Pentax DA 15mm f / 4 AL Limited prime lens compared to the Pentax DA 16-45mm f / 4 ED AL wide-angle zoom lens. A couple of test shots were taken from two meters away, with the same settings, and at the widest angle. The difference was only in the focal length: the fix has the only one - 15 mm, and this zoom has the widest - 16 mm, which is equal to 23 and 24 mm in the EGF, respectively. It is better to enlarge the pictures and watch the distortion around the edges ...

focal length 15 mm (EGF 23 mm), Pentax 15mm f / 4 Limited

Focal length 16 mm (EGF 24 mm), Pentax 16-45 mm f / 4

The wider the angle, the greater the distortion. Since the Limited has a wider focal point, it was expected that there will be a little more distortion, or, in any case, a struggle will flare up. But it did not work: the fix won unconditionally! Geometric distortion is minimal, while the Pentax 16-45 has it, which is quite expected for any zoom (and quite acceptable for a zoom of this class).

All other things being equal, the most expensive lenses are wide-angle lenses and, of course, telephoto lenses. But the most expensive of them will be high-aperture, and, of course, dustproof professional lenses with ultrasonic motors and reduced optical distortion. As a rule, such lenses are large and heavy, since they have more lenses in the optical system to eliminate aberrations.

Lenses with a focal length of a small range "around" 50 mm give less distortion, they are also called "standard" or "normal". The standard, besides the zooms, also includes some fixes, for example, "fifty rubles" (focal length \u003d 50 mm). The distortions of such fixes are very minimal, and there is one drawback (and very significant!) - there is no zoom. :)

One of the typical prime-lens schemes. Lenses of various shapes
are designed to eliminate distortion.

It is worth mentioning that in addition to focal length, lenses can be subdivided into macro lenses and portrait lenses. The distortions of the first ones are removed in the minimum focusing distance, and the second ones in the "portrait" zone (around 1.5-2 meters).

It should be remembered that on a cropped DSLR (APS-C format) the normal (or standard) focal length will be not 50, but 30-35 mm. For those who do not understand, read again about the equivalent focal length :) If it is still not clear after that, then I advise you to choose a full-frame camera, there the real focal length is equal to the equivalent, and you will not have to recalculate one into another :)

The most wide-angle compact cameras.

What is the minimum focal length for digital cameras with a non-interchangeable lens (i.e. compact)? In EGF, the wide angle of most models starts from 35-38 mm, i.e. it is not that wide. There are also those with a wide viewing angle, for example, Nikon Coolpix 5400 - the minimum focal length is 28 mm, some Panasonic models have an even smaller focal length, for example, the Panasonic Lumix DMC-FX37 - 25 mm. But you won't surprise anyone with such a wide angle.

But there are compacts with really wide-angle optics: a focal length of 24 mm (and even less!). Starting in 2010, I conducted a survey that looked like this:

"If anyone knows a compact camera with a wider angle (with a smaller focal length in the EGF) - send the name of the model, I will indicate it on the site."

Here are the names of those who sent (as promised):

Yuriy Dzyubina from Ukraine, Sergey Baum from Moscow, Afonasenkov Evgeniy from Volgograd (indicated 2 cameras), the author of this site (well, how can I not mention myself?), Yeltsov Roman from Yaroslavl, who did not want to be called "shifted" and Andronov Andrey from the Volgograd region ...

But since then a lot of compacts with a focal length of 24 mm have appeared, so I will not list all the models whose names were reported for the site by his readers. But I will point out a couple of memorable cameras.

Samsung EX1, focal length 24 mm, matrix 1 / 1.7 ", 10 megapixels, aperture f1.8 - f2.4, manual settings, weight 160 g. A camera with a very decent aperture and a rather big matrix for a compact! And the camera costs about 100 rubles for every gram :)

KODAK EASYSHARE V570 with two lenses built into the body (!). Wide-angle prime - 23 mm focal length, f2.8 aperture. The second lens is a zoom lens with a focal length of 39-117 mm and a much weaker aperture: f3.9-f4.4. This two-headed digital camera also has 2 matrices, but there seem to be no such settings as shutter speed and aperture ... But the solution is original. Weight 125 g. It could be even lighter and cheaper, if you leave 1 wide-angle fix, and remove the zoom - you would get an excellent landscape with an ideal price / quality ratio!

But there is an even shorter focal length.
Found an even wider angle: 21 mm!

02/26/2011 Casio TRYX camera. Focal length 21 mm EGF, matrix size 1 / 2.3 ", 12 Mp, aperture - f2.8. Specified by someone shifted.

07/31/2011 Found another 1 compact with the same angle! Camera Samsung WB210. The focal length of the lens is 24-288 mm, but in the special mode it gives out 21 mm EGF. Matrix size 1 / 2.3 ", 14 Mp, aperture - f2.9-f5.9 (and f3.4 in 21 mm mode). Pointed camera Andronov Andrey, Volgograd region.

08/28/2013 Found a compact with an even wider angle! LUMIX DMC-FZ72 camera. The focal length of the objective is 20-1200 (!) Mm, apparently the world's largest superzoom (60x). Matrix size 1 / 2.3 ", 16.1 Mp, aperture - f2.8-f5.9, manual settings, weight: 606 g. Specified camera Victor, Kemerovo.

For 2013 the widest focal length compact
has LUMIX DMC-FZ72 - 20 mm in EGF!

This is how we all together search and find the widest angle!

Five years have passed, and a wider angle than 20 mm has not been found (perhaps this is the limit for compact cameras). However, I received a letter about another camera with an EGF 20 mm.

04/04/2018 The focal length of the lens is 20 mm with a viewing angle of 94 °. The FC330 camera as part of the DJI Phantom 4. The matrix size is 1 / 2.3 ", 12.4 Mp, the aperture is f2.8. The camera was indicated by someone who wished to remain incognito.

For 2018, the widest focal length of 20 mm in EGF from compacts
have only 2 cameras mentioned above.

Knowing what focal length is and what the features are is especially important when buying lenses. This tutorial will give you information on how lenses with different focal lengths work, how to use them creatively and choose the ones that are right for you.

Step 1 - What does this actually mean?

The focal length of your lens basically determines what scale of the image will appear in your photographs: the higher the number, the greater the effect of zooming in and out.

Focal length is often misunderstood as being measured from the front or rear lens. This is actually the distance from the point of convergence to the sensor or film in the camera. Take a look at the diagram below where it is explained

Step 2 - different focal lengths and how they are used

Ultra wide angle 12-24mm

These lenses are considered highly specialized and are not often included with the lens of the general photographer. They create such a wide angle of view that the image can look distorted, as our eyes are not used to this kind of range. They are often used in event and architectural photography, for shooting in confined spaces. Wide-angle lenses seem to place the photographer in the center of events, making him no longer an observer, but a participant, creating the effect of presence. They are not very suitable for portraits, as they increase perspective so much that facial features can be distorted and look unnatural.

Wide angle 24-35mm

Here you will find many complete lenses for full frame cameras, they start at 24mm when the angle is wide, but distortion is not yet as pronounced. These lenses are widely used for reportage photography, photojournalists for documentary filming, because they have a wide enough angle to include a large number of objects, and thus the distortion is not so significant.

Standard 35-70mm

It is in this range of focal lengths of 45-50 mm that the angle of view of the lens will roughly correspond to how our eyes see (excluding peripheral vision). I personally would like to use this range when shooting outdoors or when meeting friends in the pub or at the dinner table. A standard lens such as a 50mm f / 1.8 is a great inexpensive and gives excellent results. A fixed focal length lens will always give best quality images than zoom. This is because it is built with a single purpose. He does one job well and several jobs bad.

Initial telephoto 70-105mm

This range is usually the extreme for supplied lenses. Telephoto lenses and prime lenses for portraits (about 85 mm) begin with it. It is a good choice for portraits, as it can shoot close-up portraits without distortion, and also get the separation of the subject from the background.

Tele 105-300 mm

Lenses in this range are often used for distant scenes such as buildings, mountains. They are not suitable for landscapes as they compress the perspective. Longer lenses are mainly used for sports or wildlife photography.

Step 3 - How does focal length affect perspective?

I talked about this in the previous section, but to give you a better idea of \u200b\u200bthe effect of focal length on perspective, I took 4 photos of the same subjects at different focal lengths and compared them. Three items (soup cans) were in the same position 10 cm apart in each photograph. It is worth noting that the pictures were taken with a crop camera, so the focal length will be slightly longer.

Now let's talk about what the crop factor is. In essence, this means that if any lens for a full frame (EF, FX, etc.) is placed on a crop factor carcass, then part of the image will be cropped. The cropping factor will be approximately 1.6. In real terms, this means that if you shoot with a 35mm lens, you will get the result as if you were shooting with a 50mm lens.

How it works is shown in the pictures below. This is actually a zoomed image, narrowing the angle of view of the lens.

Even lenses that are designed for crop cameras (EF-S, DX) will have a similar effect, since focal lengths are always quoted for a full frame. It's just that these lenses are on full frame will give a strong vignetting effect, since the image is not projected over the entire area of \u200b\u200bthe frame.

That's all! And two more completely different shots taken at different focal lengths. The first at 24mm, the second at 300mm (both on cameras with a crop sensor).

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