What is a 35mm focal length for? Focal length and perspective. Influence of focal length on the degree of 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 less, zooming more.

Understanding terminology

To put it as simply as possible, focal length lens is the distance from the lens to the focal point on the film or sensor. In this case, the depicted object must be at a sufficiently large distance. The human eye is built in much the same way as a lens. We see everything around at an angle of 45 degrees. A normal or standard lens sees everything at 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

The standard has always been considered a focus indicator of 35 millimeters. However, modern digital technology can be supplied with a matrix, which is equal in size to a 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 ones. It is worth talking about this standard. In accordance with the Pythagorean theorem, the diagonal of the frame 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, in which this parameter is 50 mm. It's much more interesting if the focus value is less than or greater than this. If the focal length of the lens is 8-20mm, then it will be referred to as ultra wide angle, allowing you to shoot in full height in a cramped 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 lenses. For telephoto lenses, the focal length is from 100 to 1000-1200 mm. Some companies produce models in which this value is 2000 mm. With their help, you can shoot very, very distant objects.

Selection Tips

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 of a field of view you require. Sometimes 18mm is enough. It is worth starting with a wide angle, as there is always a need for one, 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 you will need an even wider-angle solution, that's when you can turn your attention to zoom lenses. It is worth saying that there are quite a lot of starting values. When choosing the best option, you should look at reviews about a particular lens, as well as photos that can be obtained with it. It is most correct if you have two lenses in your arsenal, one of which overlaps the other in focus value.

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

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

In order to deal with 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 lens of the objective (not one, but several lenses are installed in the lenses, but for now we will not complicate it). Since the object being photographed is usually located at a considerable distance from the lens, the rays of reflected light can be considered parallel to each other.

When passing through the lens, the rays are refracted and at some distance from it they "gather" 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 passing 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 a camera matrix can be represented like this:

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

We have considered the physical meaning of the concept of “focal length”, but if you do not go into the details of optics and forget about physics in general, then the focal length determines how much the lens will be able to “zoom in” on the subject. Therefore, you can remember one simple rule:

the longer the focal length of the lens, the visually closer will be the object being photographed in the photo

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

Various frame coverage angles

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 35mm film, focal lengths of 40mm to 60mm generally correspond to the perspective picture perceived by the human naked eye.

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

* The relationship between focal length and field of view angle 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 object, the angles of coverage of the frame field may differ.

perspective

The lens displays nearby objects as larger, and distant objects as smaller. When using a wide-angle lens, the focal length is shorter, and this effect is enhanced, i.e. close-up objects are shown large, and distant objects very small (enhanced perspective).

When working with telescopic lenses, the opposite effect is observed, that is, distant parts of the scene are reproduced somewhat more, and close parts are somewhat smaller than what 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 are also displayed sharply. This range is called the sharpened space range. If it is small, they say "shallow depth of field", and if it is large, they say "large depth of field".
The range of sharply displayed space becomes smaller as the set f-number decreases (i.e. when the f-stop opens!), and vice versa. In addition, with the same distance setting, the depth of field is the smaller, the longer the focal length of the lens.

Comparison of a zoom lens and a fixed focal length lens

The zoom lens is versatile

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

Lenses with fixed focal length and maximum image quality

A fixed focal length lens can be optimally applied to its specific area, combining compactness with exceptionally high image quality. Tamron offers a range of prime lenses that successfully take advantage of technologies originally developed for zoom 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),
Reflex lens (500mm F/8) (supplied as a manual focus lens only).

Macro (close-up shots)

Dedicated macro lens

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

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 larger the X number, the smaller part of the original object is displayed on the film. The coin displayed on the film with the same size as in reality (life size) is reproduced in the display scale 1:1. A display scale of 1:2 means that it appears on film only at half its true size.

Close-up with a ZOOM lens

As mentioned above, macro photography is a method of displaying small objects in a photograph. Close-ups are possible not only with special lenses, but also with telescopic lenses that have a variable focal length (ZOOM lenses), provided that the telescopic lens has the appropriate setting. Tamron lenses with the designation "MACRO" on the barrel allow you to get a display magnification of at least 1:4.

solar hood

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

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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 smaller 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 are more separate view fisheye lenses). Here is an example photo (from here) taken with a wide angle " fish eye with a focal length of 8mm.
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 camera Finepix X20, 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, Sony cameras RX10, where the physical range is 8.8-73.3, and on the installed 2.7 crop, you get an excellent range of 24-200 mm: 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 focus point (in mm), i.e. to the film (matrix), where a sharp image of the object is formed. For example, focal length 50, or 120 mm. And what, exactly, is the difference? The difference lies in the choice of frame boundaries. Let's see what pictures can be taken from the same shooting point: 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

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 bring the subject of photography closer (or, conversely, reduce it). Even simpler: what is more than 50 mm, we increase, everything that is less than 50, we reduce. And, quite simply: a focal length of 100 mm is a 2-fold increase, 180 mm is an increase of 3.6 times. Easier nowhere. But why was 50 mm chosen as the reference 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 eyes covers a much larger angle). They also consider that a standard lens has a focal length of 50 mm, since this is close to the diagonal of a film frame (43 mm). Do not look for difficulties in this. Sometimes they are created only in order to successfully overcome them later :)

How to find the focal length of a lens

This has already been discussed in the article "Lenses", we will repeat for those who came here from other pages. How to find the focal length? Very simple. The focal length is indicated on the barrel of the lens, next to it is indicated 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 f2 aperture (marked 1: 2). I indicated the focal length in the photo with a yellow arrow.

What else can you tell about the lens, looking at its designations? A little.

This Helios model has a "K" bayonet mount (it will fit a Pentax DSLR without any adapters), multi-layer coating, a fixed focal length of 58 mm, f2 aperture, a mounting thread for filters - M52x0.75, the lens itself was produced for Zenith cameras with a "K" mount "at the Krasnogorsk Mechanical Plant, the latter is indicated by the icon of a prism 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 this characteristic is often mentioned in stores. Actually, what is zoom? A zoom is a lens with a variable focal length, it is also a "zoom", it is also a "vario lens" - there are many names, but the meaning is the same. And more precisely, complete absence such :) For example, we have a typical focal length of the lens 28-55 mm. Divide 55 by 28 and get approximately the number 2. This means a 2x zoom :) This figure is absolutely of no use, because, for example, a 100-200 mm zoom lens also has a 2x zoom, but these are completely different lenses , with a different angle of view and for completely different tasks. In this regard, only the focal length is a useful characteristic, so let's return to studying it, and forget the marketing word zoom, or we will use it not for meaningless calculations, but only to designate a zoom lens. That's why:

A zoom is a lens that has a variable focal length. And no more!

The zoom, of course, is convenient, but in the red at the long end of the zoom, the aperture ratio almost always drops (especially with cheap optics). For example, a 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. as the focal length increases, the aperture will fall! Therefore, one small tip: do not chase a huge zoom! There are digital compacts (we read - a small matrix!), With a 20-30x (and even more) zoom. And here, when shooting at the long end of the zoom, the lens aperture closes abruptly, as a result, less light enters. This means that fast shutter speeds will become unavailable, and shooting at long shutter speeds (not using a tripod) will lead to shake and blurry shots; either automation (or you) in response increases the sensitivity of the matrix, i.e. increases the signal on it, and the small matrix of the camera makes noise, but what is the result? Disgusting pictures. Therefore, choose a 3-4x zoom, otherwise, if you are not going to work with a tripod, it will be money thrown away!

It's not a zoom lens, it's a fixed focal lens, it's a discrete lens ... did I miss anything? Yes! He is a lens with a fixed focal length :) You have already seen the fix in the Helios picture above. Once upon a time, 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 2.8, was a standard lens for the Zenit-6 camera.

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

Focal length in 35 mm equivalent (EGF)

There are two focal lengths - real, and equivalent to cameras of 35 mm format. The real is indicated on the lens, the equivalent does not exist in nature, it is calculated. Why such difficulties and why is it necessary? 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 dollars), then the lens, say, at 28 mm was called wide-angle, 70-100 mm - portrait, and over 100-150 mm - telephoto (or telephoto lens). This division was conditional, but it was understandable and suited everyone - some had a wider angle of vision, others had a narrower one. Actually, we are talking about the angle of view of the lens, it’s just that “bad” photographers confuse a beginner with terrible terms: “focal length”, “equivalent focal length”, “EGF”, “Matrix crop factor”, just “crop”, and other rubbish that has only a side relationship to the angle of view of photography, and hence the composition of the frame :) In general, in the era of 35 mm film, it was easier to compare lenses and take pictures, and not nonsense :)

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

What is 35 mm format? 35 mm is the width of the film including the perforated part.

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

However, with the advent digital cameras the situation has changed. If digital cameras had the same matrix size - 24 x 36 mm, then there would be no difficulties in comparing lenses. But this size digital cameras have only very expensive professional-grade DSLRs. Amateur DSLRs have a matrix size 1.5-2 times smaller than "full-size", and digital compacts are even smaller than amateur ones. Such cameras are considered non-35 mm format and, depending on the size of the sensor, are designated APS-C, 4/3, and others. 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 sensor sizes. To avoid confusion, we decided to introduce the term "equivalent focal length" (EFF), i.e. focal length for cameras of 35 mm format - to compare with a photographic film having a width of 35 mm and a frame size of 36x24 mm. As a rule, the actual focal length is indicated on the lens, and in the user manual you can find out which EGF it corresponds to. Sometimes this can be found in short description cameras in the store.

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

EGF is used only to compare camera lenses with different crop factor - comparisons in the angle of view. The terminology here 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 has become the same as if the focal length were 75 mm. It turns out that's what. Yes, the focal length of the entire system has changed (the lenses themselves have not!), but the distortions within this lens have not changed, since they were "sharpened" for 50mm, not 75.

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

If the size of the matrix is known, then the equivalent is easy to calculate. How many times the camera's matrix is smaller than the film frame, then the real focal length must be multiplied by so much to find out the equivalent. This difference (more precisely, 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 approximately 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, which is 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 universal lens - there is a wide angle for landscapes, and on a long one you can at least shoot portraits! It’s a pity that the whale has a weak aperture, but that’s a completely different conversation.

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

Those. when the matrix of such cameras has an unequal 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 look at the multiplier (or crop) for typical photosensitive sizes camera elements:

Company	Designation	Size mm	crop
FED	film 35 mm	36mm x 24mm	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	7.2x5.3	4.8
compact	1/2.5	5.8x4.3	6.2
compact	1/3.2	4.5x3.4	8

As for the compacts, they have matrices 4-8 times smaller than the size of a film frame! For example, a typical 1/2.5"" matrix has a size of 5.8 mm along the wide side, i.e. 6.2 times smaller than the 36 mm side of the film. The lens of such a camera with a focal length, for example, 5.6 - 17.7 mm, will correspond to 35 - 110 mm EGF. Let's take a 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 focal length lens, and the DSLR has 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 clearly see how meaningless the word zoom, or rather the zoom ratio :) The focal length rules!

focal distance	lens	photography purposes	vision angle
4 - 16 mm	fish eye	landscape, art, special physical landscapes	180° or more
10 - 24 mm	above- wide-angle	interior, landscape, intention- nee 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 anything!	46° (32 - 62)
65 - 300 mm	telephoto lens	portrait, sports 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’s good to shoot a landscape with a wide-angle lens: such optics have a higher depth of field, and more will fit at a wide shooting angle). 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 required to emphasize the expressiveness or dynamics of the plot. And it is convenient to zoom in with a telephoto lens, i.e. zoom in on a hard-to-reach subject. For example, the muzzle of a lion in the wild and in the whole frame :) A wide-angle lens has a focal length of less than 35 mm, a standard 35-65 mm, a 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 generalists is that they are inferior to a specialized one (for example, a telephoto lens), as a rule, in aperture ratio, or in maximum focal length, or in price (with the same aperture ratio, the price will be higher), or in quality.

A simple (nowhere easier!) The picture on the left will help you learn 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 or scene being filmed. This division is, of course, highly arbitrary. Landscapes are also shot with a long telephoto lens, and everything is shot with a wide-angle lens, even up to portraits.

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 such a one!), And end up with a huge choice of focal lengths, here you have wide-angle + standard + telephoto + very large telephoto, and all happiness in one vial.

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

Focal length and aberrations

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

The best in this regard will be a fix - a lens that has a fixed focal length (it has only one). Distortion in this is easier to remove than in zoom. In addition, fixes are distinguished by greater aperture ratio, smaller dimensions, and the most worthy price / aperture 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 tightly clamped apertures). The most typical example for a wide-angle lens is distortion. The wider the angle and span of the zoom, the more the so-called. barrel distortion (if not corrected with additional lenses). To better understand this contraption, we look at the picture.

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

Below is an example of geometric distortion (barrel distortion) of a very expensive Pentax DA 15mm f/4 AL Limited prime lens compared to a Pentax DA 16-45mm f/4 ED AL wide-angle zoom lens. A couple of test shots were taken from about two meters, 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 see 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 more distortion. Since the Limited has a wider focal length, it was expected that there would be a little more distortion, or, in any case, a fight would flare up. But it did not work out: the fix won unconditionally! Its geometric distortions are minimal, while Pentax 16-45 has it, which is quite expected for any zoom (and quite acceptable for a zoom of this class).

Other things being equal, the most expensive lenses are those with a wide angle and, of course, telephoto lenses. But the most expensive of them will be fast, and, of course, dust and moisture-proof 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 scheme to eliminate aberrations.

Lenses with a focal length of a short range "around" 50 mm, they are also called "standard" or "normal" lenses, give less distortion. In addition to zooms, the standard ones also include some fixes, for example, "fifty kopecks" (focal length = 50 mm). The distortions of such fixes are the most minimal, and there is only one drawback (and very significant!) - there is no zoom. :)

One of the typical schemes of a fixed lens. Lenses of various shapes
designed to eliminate distortion.

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

It must be remembered that on a cropped DSLR (APS-C format), the normal (or standard) focal length will not be 50, but 30-35 mm. Whoever doesn’t understand, we read again about the equivalent focal length :) If after that it’s not clear, then I advise you to choose a full-frame camera, where the real focal length is equal to the equivalent one, and you don’t have to recalculate one into another :)

The world's widest compact cameras.

What is the minimum focal length for digital cameras with a fixed lens (i.e. for compacts)? In EGF, the wide angle of most models starts from 35-38 mm, i.e. it's not that wide. There are also those with a large viewing angle, for example, Nikon Coolpix 5400 - a minimum focal length of 28 mm, some Panasonic models have an even shorter focal length, for example, 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 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, Evgeniy Afonasenkov from Volgograd (he indicated 2 cameras), the author of this site (well, why not mention himself?), Roman Eltsov from Yaroslavl, who did not want to be called “shifted” and Andrey Andronov from the Volgograd region .

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

Samsung EX1, focal length 24 mm, 1/1.7" matrix, 10 MP, 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 per gram :)

KODAK EASYSHARE V570 with two built-in lenses(!). Wide-angle prime - focal length 23 mm, aperture f2.8. 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 double-headed digital camera also has 2 matrices, but it seems that there are 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 shot with an ideal price / quality ratio!

But there is an even shorter focal length.
An even wider angle was found: 21 mm!

02/26/2011 Casio TRYX camera. Focal length 21 mm EGF, matrix size 1/2.3", 12 MP, aperture - f2.8. Some shifted pointed out.

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

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

For 2013, the widest-angle focal length of the compacts
has LUMIX DMC-FZ72 - 20 mm in EGF!

So together we are looking for and find the widest angle!

5 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 EGF 20 mm.

04/04/2018 The focal length of the lens is 20 mm with a viewing angle of 94°. Camera FC330 as part of the DJI Phantom 4 quadrocopter. Matrix size 1/2.3", 12.4 MP, aperture - f2.8. Someone who wished to remain incognito pointed out the camera.

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

Knowing what focal length is and what the features are is especially important when buying lenses. This lesson 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 it really mean?

The focal length of your lens basically determines what zoom will be in your photos: the larger the number, the greater the effect of zooming in and out.

Focal length is often misunderstood, saying that it is measured from the front or back of the lens. It is really the distance from the convergence point to the sensor or film in the camera. Look at the diagram below where this 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 in the general photographer's lens kit. They create such a wide viewing angle that the image may look distorted because 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, as it were, 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 portrait photography, as they increase the perspective so much that facial features can be distorted and look unnatural.

Wide angle 24-35mm

Here you will find many kit lenses for full frame cameras, they start at 24mm, when the angle is wide, but the distortion is not yet so pronounced. These lenses are widely used for reportage photography, documentary photojournalists because they have a wide enough angle to include a large number of objects, and yet the distortion is not as 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 a pub or at a dinner table. A standard lens such as the 50mm f/1.8 is a great value lens and gives excellent results. A fixed focal length lens will always give the best quality images than zoom. This is because it is built with a single purpose in mind. He does one job well and several jobs poorly.

Initial telephoto 70-105mm

This range is usually the extreme range for kit lenses. It starts with telephoto and prime lenses for portraiture (about 85 mm). This is a good choice for portraiture as it can capture close-up portraits without distortion, as well as getting subject-to-background separation.

Tele 105-300 mm

Lenses in this range are often used for distant scenes such as buildings and 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 already talked about this in the previous section, but to give you a better idea of the effect of focal length on perspective, I took 4 photos of the same objects at different focal lengths and compared them. Three objects (soup cans) were in the same position 10 cm apart in each photo. It is worth noting that the pictures were taken on a crop camera, so the focal length will be slightly larger.

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 put on a carcass with a crop factor, then part of the image will be cut off. The crop factor will be approximately 1.6. In real terms, this means that if you shoot with a 35mm lens, you will get the same 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 experience a similar effect, as focal lengths are always specified for full frame. These lenses are just full frame will give a strong vignetting effect, since the image is not projected over the entire frame area.

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

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