Operating principle of the teleconverter

Teleconverters

A teleconverter or extender is a small optical device installed between the camera and the lens to increase the focal length of the lens. The effect of changing the focal length is achieved by increasing the central part of the image projected by the lens onto the camera matrix, which leads to a decrease in the image angle.

Teleconverters are resorted to mainly because of stinginess (or, if you prefer, reasonable frugality), namely in those cases when the photographer wanted to use a lens longer than those he had available, but at the same time buying a new lens with the required focal length seems to him not entirely justified economically. A compact and relatively inexpensive teleconverter can help not only reduce financial costs, but also reduce the amount of photographic equipment carried at one time. Unfortunately, the use of extenders is fraught with a number of not very pleasant compromises.

Disadvantages of teleconverters

The main and most obvious negative effect is a drop in lens aperture proportional to the square of the teleconverter magnification. Thus, a double teleconverter, doubling the focal length of the lens, reduces the amount of light falling on the matrix by four times, i.e. by 2 EV. What does this mean in practice?

Firstly, autofocus performance deteriorates. The darker the lens, the worse the autofocus does its job. Most modern cameras have autofocus sensors designed to work with lenses with an aperture of at least f/5.6. Some models retain the ability to autofocus up to f/8, however, only sensors located in the very center of the frame will work. Obviously, if we take a lens with a native aperture of f/5.6 and add a 2x teleconverter to it, the final aperture will drop to f/11, completely paralyzing autofocus. It is easy to conclude that in order to maintain autofocus performance when using teleconverters, you should give preference to lenses with an initially high aperture ratio, and also abandon extenders with excessive magnification.

Secondly, reducing the relative aperture may require a proportional increase in shutter speed, which, in turn, often leads to blurred images. This is especially true when shooting handheld, since increasing the focal length requires us to decrease the shutter speed to prevent movement, and we, on the contrary, are forced to increase the shutter speed due to a drop in aperture ratio. You have to either raise the ISO or shoot with underexposure.

But even if we leave aside the negative effects associated with a decrease in aperture, the use of teleconverters will still be associated with a deterioration in image quality. The lens is a fairly complex, carefully balanced optical system, to which it is simply impossible to add several additional lenses without affecting the final image. A drop in sharpness and contrast will always occur, the only question is how noticeable it will be. When using teleconverters with a low magnification ratio (1.4x) together with high-aperture long-focus primes, the image quality will hardly suffer. If you take a three-fold extender and set it to normal zoom, then image degradation will be obvious.

In addition, the teleconverter introduces additional mechanical play into the system, which, although small, can affect focusing accuracy, which means that after installing the teleconverter, it is imperative to go through the autofocus fine-tuning procedure.

I also advise you to avoid third-party teleconverters and opt for teleconverters from the same brand as your lenses. Nikon or Canon know the features of their optics and take them into account when developing extenders. Third-party manufacturers will never be able to take into account all the nuances and achieve completely consistent operation of the teleconverter and lens.

What lenses can teleconverters be used with?

The only category of lenses, the use of teleconverters together with which is completely justified, is super telephoto lenses, i.e. relatively fast long-focus primes, like 300mm f/2.8 or 500mm f/4. Firstly, such lenses are obscenely expensive and a rare photographer can afford a set of exotic telephoto lenses, while teleconverters allow you to vary the focal length without large financial costs. Secondly, due to the design features, super-telephoto lenses tolerate cooperation with teleconverters with minimal consequences for image quality.

The use of teleconverters in conjunction with long zooms (70-200mm f/2.8, 200-400mm f/4) is also acceptable, but with some caution.

As for normal and even more so wide-angle lenses (both zooms and primes), it’s better not to think about teleconverters here. There are several reasons for this.

First, the rear element of a normal or wide-angle lens is usually located very close to the mount shank. At the same time, the front element of the teleconverter often protrudes beyond its body. As a result, the objective and extender lenses may simply collide with each other. Fortunately, good teleconverters are usually designed in such a way that it is physically impossible to install an unsuitable lens on them. If you still want to do this, then you will have to first disassemble the teleconverter and grind off one of the bayonet blades with a needle file.

Secondly, the optical design of teleconverters is designed for use exclusively in combination with telephoto lenses, and therefore the results of experiments with short-focus lenses will be, to put it mildly, suboptimal.

Third, you almost always get performance that you could get from just one of the existing lenses. For example, adding a 1.4x converter to a 16-35mm f/4 lens (assuming you managed to bypass fool proof) will give you a ridiculous 22.4-49mm f/5.6. For what?! Are there not enough inexpensive lenses with excellent optics in this range?

Teleconverters are used when there is no other option, or when this option is associated with excessive costs. In all other cases, it is better to do without teleconverters.

Various teleconverters and changing lens parameters

Let's take a closer look at some types of teleconverters.

The only representative - Nikon TC800-1.25E ED is supplied with the AF-S NIKKOR 800mm f/5.6E FL ED VR lens and is not compatible with other lenses. Increases focal length by 1.25 times, reduces aperture by 2/3 stops. This turns an 800mm f/5.6 lens into a 1000mm f/7.1 lens.

The most practical type of teleconverter. Representatives: Nikon TC-14E ​​III, Canon Extender EF 1.4x II, as well as the built-in teleconverter in the Canon EF 200-400mm f/4L IS USM Extender 1.4X lens. Increases focal length by 1.4 times, reduces aperture by 1 stop. For example, a 200mm f/2 becomes a 280mm f/2.8.

Nikon TC-17E. Increases focal length by 1.7 times, reduces aperture by 1.5 stops. For example, a 200mm f/2 becomes a 340mm f/3.3.

Representatives: Nikon TC-20E III, Canon Extender EF 2x III. Increases the focal length by 2 times, reduces the aperture ratio by 2 steps. For example, a 200mm f/2 becomes a 400mm f/4.

I strongly do not recommend that you resort to teleconverters with a multiplicity greater than 2, especially since such teleconverters are extremely rare nowadays, and even then only from third-party manufacturers.

So that you don't have to do the calculations for each lens, I have compiled a small table showing the change in focal length and lens speed when using 1.4x, 1.7x and 2x teleconverters.

Initial lens parameters

Using a teleconverter

1.4x

1,7x

2x

70-200mm f /2.8

70-200mm f /4

80-400mm f/4.5-5.6

100-400mm f/4.5-5.6

200-400mm f /4

200-500mm f/5.6

200mm / 2

200mm f /2.8

300mm f /2.8

300mm / 4

400mm / 2.8

400mm / 4

400mm f /5.6

500mm / 4

600mm / 4

800mm f /5.6

The TC800-1.25E converter is unique, and therefore there is no 1.25x column in the table. Dashes mean that this combination either does not occur in nature at all, or its use is devoid of practical meaning. In particular, this applies to those cases when the final aperture is below f/8. In fact, even f/8 is a marginal value at which autofocus will only work on some cameras, and even then not in the best way. I would advise you not to drop the aperture below f/5.6.

Teleconverters or cropping?

Given the absolutely insane number of megapixels in modern cameras, simply cropping the image seems like a completely reasonable alternative to using teleconverters. Cropping, unlike a teleconverter, does not affect the sharpness or aperture of the lens. The only downside is that you will get an image with a lower resolution than if you took a teleconverter, however, the resolution remaining after cropping is usually more than enough. In fact, if we take a frame with a resolution of, say, 36 megapixels and enlarge the middle by 1.5 times, we will still have 15 megapixels left, and believe me, this is a lot.

Thank you for your attention!

Post scriptum

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Please remember that this article is subject to copyright. Reprinting and quoting are permissible provided there is a valid link to the source, and the text used must not be distorted or modified in any way.

How does a teleconverter work? Review of Soligor AF PRO 1.4x teleconverter

A teleconverter is a special device that helps increase the focal length of a lens.

Teleconverter - article from Radozhiva

In fact, the focal length of a lens is a physical quantity and it simply cannot be increased. But due to the fact that a lens with a converter behaves completely differently, it is convenient to say that the teleconverter changes the focal length of the lens.

What is a teleconverter used for?

The answer is very simple - to increase the focal length of the lens . For example, you have a 55-200mm telephoto lens, and desperately need a stronger zoom. There are two options - either buy a new lens or buy a converter. With a 2x teleconverter you can achieve a focal length of 400mm with the same lens. It is very comfortable. The teleconverter can be used with any lens. If you have several lenses, you can increase the focal length of any of them.

How does a teleconverter work?

The teleconverter actually enlarges the image from the center of the picture (the center of the lens). This results in a visible increase in focal length. The teleconverter is installed between the camera and the lens . Usually, I install the teleconverter on the lens, and then install the resulting bundle on the camera. On one side, the teleconverter has exactly the same bayonet connector as the camera. On the other hand, it has exactly the same mounting connector as the lens.

The difference in focal length is 1.4 times. The place from which they filmed is the same.

Magnification ratio

Teleconverters are mainly characterized by their magnification ratio. For example, the most common teleconverters have a magnification of 1.4X, 2X, 3X . This means that when using a lens with a converter, the focal length of such a combination will increase by 1.4 or 2 or 3 times, depending on the teleconverter.

Usage example

If I use a 1.4x teleconverter with a 50-200mm lens, the result will be a lens with a focal length of 70-280mm. And if you use a 2X converter with a 70-300mm lens, you will get a 140-600mm lens. And 600mm is already really impressive.

Attention , keep in mind that by increasing the focal length, you thereby reduce the value of the relative aperture . If the teleconverter magnification is 2x, then in addition to doubling the focal length of the lens, the aperture number will also increase by 2 times. And pay attention, the catch is that the difference in power will not change by 2 times, but by 2 stops - that is, 4 times.

Therefore, a teleconverter with a magnification of 1.4x reduces the aperture ratio by 2 times (exposure, all other things being equal, drops by 1 stop). A teleconverter with a 2X magnification reduces the aperture ratio by 4 times (exposure, all other things being equal, drops by 2 stops). And the 3X teleconverter reduces the aperture ratio by 9 times (exposure decreases by more than 3 stops). It turns out that with a teleconverter with a power of 3x, the focal length increases by 3 times, but the aperture ratio drops by 9 times. The drop in aperture ratio is equal to the square of the teleconverter's magnification, for example, with a magnification ratio of 1.7X, the aperture ratio will decrease by 1.7 * 1.7 = 2.89 times (actually 3 times, since 1.7 approximately corresponds to the square root of 3). Such subtle tricks can rarely be found anywhere, so be careful about the loss of aperture when purchasing a teleconverter .

Let me explain in more detail. We wanted to shoot the moon, so we took a 2x teleconverter and attached it to a 300mm F5.6 lens, after which the lens turned into a 600mm F11.2. If we were shooting the moon at 300mm F5.6 and at any one ISO value, let us have a shutter speed of 1/80s. Shooting the same moon at 600mm F11.2, we get a shutter speed of 1/20s. The difference in shutter speed is 4 times, and the difference in focal length is 2 times. But for a long focal length this is very critical and we cannot do without a tripod. You can read about the importance of shutter speed at long focal lengths in the article on how to take handheld photographs.

View of the lens with a teleconverter installed

Types of teleconverters

Converters for cameras come in mainly two types - with autofocus support and without autofocus support . Both types can be used equally well for taking photographs. The only thing is that converters without autofocus support will not allow you to get autofocus with your lens. Nikon has another type of converter that supports communication between the camera and the lens, but for lenses with autofocus but without a focusing motor, they cannot provide autofocus. Also, good teleconverters record the increased focal length and aperture value in EXIF ​​image data, so the camera understands that the aperture is quite small when using a teleconverter, but the focal length is large.

More nuances

There are converters that are installed in front of the lens as an attachment. Most often, such converters provide a wider viewing angle. Often used on video cameras. Converters can be installed on the lens sequentially and you can achieve a simply super huge increase in focal length. Also, many cameras cannot focus properly with apertures below 5.6 - read about this in the specifications of your camera. For example, Nikon D4 can focus at apertures up to 8.0

Useful tips

A good teleconverter is quite expensive because it can change the focal lengths of all your lenses. Sometimes it is better to buy a good telephoto lens outright rather than a cheap telephoto lens and a cheap teleconverter. Typically, a teleconverter enhances the shortcomings of lenses; you need to look especially carefully at increased aberrations and drops in sharpness . Also, the teleconverter can change the white balance settings - change the color gamut produced by the lens. But, at the same time, a teleconverter can rid the image from the lens of excessive distortion .

Let's see how much a teleconverter affects the quality of a photo using a real example of a teleconverter

Review of the Soligor AF PRO tele-converter AFd 1.4x N/AFd

Review of the Soligor AF PRO tele-converter AFd 1.4x

Let's now get acquainted with the operation of the teleconverter in practice, and at the same time draw a few conclusions for ourselves about the quality of my Soligor 1.4X AF/D APO. This teleconverter showed good picture quality when working with different lenses.

Two test shots on Soligor tele-converter 1.4x

Below are crops (clippings) of parts of the image in proportions of 1 to 1, so that you can judge the sharpness and HA.

Cropped images for the tele-converter test

The test was carried out from a tripod, focusing through Live View, several test shots were taken and the best were selected to achieve the most objective conclusion. The shooting was done using the ML-L3 remote control. As you can see, the sharpness has suffered. Also, keep in mind that when you change the focal length, the composition of the frame changes and the exposure metering will be different, so the automation may show a decrease in shutter speed not exactly 2 times, but more or less.

The advantage of this teleconverter is the fact that it will focus almost all lenses without a built-in AF focusing motor, as well as all lenses with a built-in AF-S motor. I used this teleconverter with the Nikon 50mm F1.8D AF motorless lens without any problems. The teleconverter has virtually no effect on focusing speed, just like it has no effect on correct focusing. The teleconverter also transmits the desired value from the camera through the aperture lever. The converter is very easy to attach and remove from the lens and camera, well assembled, small and weighty.

The disadvantage of this teleconverter is that it is not possible to multiply the focal length and aperture by 1.4 to transfer them to the camera, so the camera sees that it simply has a native lens installed on it without any converter. Also, the lenses give off a slightly yellow color, this distorts the native color rendition of the lens .

conclusions

A teleconverter is a very useful tool for a photographer who needs long focal lengths. It must be remembered that in addition to increasing the focal length of any lens, a teleconverter reduces the lens aperture. Soligor 1.4X AFD APO teleconverter (from this review) allows you to automatically focus on any AF and AF-S lens from Nikon and has good performance.

If you have a question, ask in the comments. Thank you for your attention. Arkady Shapoval.

Teleconverter

The adapter rings described in the previous article, connected by wires, allow you to control the lens regardless of where it is installed. Thus, we can now easily install attachments not only in front of, but also behind the lens. The first thing that comes to mind is to use a Barlow lens to change the focal length of the lens. The negative lens, located behind the telescope lens, went down in history after the name of Peter Barlow (1776 - 1862) who proposed this design in 1828. Barlow's role in physics and mathematics is very significant. He conducted research on magnetism, compass deviation, created a unipolar motor, and created mathematical tables of basic functions (squares, reciprocals, roots, etc.). How significant exactly his contribution to optics turned out to be is difficult to say with certainty, since the combination of a positive and negative lens was known 200 years earlier; in 1610, some Dutch created a telescope, having learned about the existence of which, Galileo repeated it. And by whose name she went down in history. In a Galilean tube, the focal points of the positive and negative lenses coincide. Afocal attachments, installed to change the focal length of the system in front of the lens, have the optical design of a Galileo tube. In a Barlow optical system, the negative lens can move. We can say that if you take Galileo’s telescope, move the eyepiece and place the resulting structure instead of a lens in Kepler’s telescope (in the treatise “Dioptrics” (1611), Kepler described the telescope he invented), you will get a telescope with variable magnification, i.e. in order to change the focal length, we do not need to make a new lens with a different surface curvature, but we can simply move the components relative to each other. As a child, I had an optical construction kit that consisted of a set of plastic lenses that made it easy to create a Kepler tube, a Galilean tube, a microscope, and much more. At the same time, the supplied frames practically did not allow for mistakes, and the necessary design was obtained absolutely thoughtlessly. But the most interesting thing is that this construction set included a mock-up of an optical bench, which allowed you to place lenses in any order. It is very likely that in the 200 years between Kepler's and Galileo's tubes and Barlow's optical system, someone has already shuffled his existing lenses and tried a similar design. But it went down in history as the Barlow lens, and the date of its creation is considered to be 1828.

It is not obvious that this particular design became the direct ancestor of zoom lenses. But their designers certainly knew that by moving the negative lens in a telescope, we can change its effective focal length. The calculation of the optical design using a Barlow lens is described in detail in the book by L.L. Sikoruk. “Telescopes for astronomy enthusiasts”, namely in Chapter 3.4. I note that most modern lenses already contain a negative lens in their design, which is used to change the focal length of the system. In telephoto cameras, this is a desire for compactness, and in wide-angle lenses, built according to the reverse telephoto lens design, this is due to the need to provide a large working distance. I wrote more about this ten years ago in the article Why are there so many lenses in a lens?

Let me briefly illustrate the theory:

In photography, the Barlow lens is known as a teleconverter. The movement of the lens in SLR cameras is limited by the working distance of the device, and it is usually not possible to obtain several teleconverters with different magnification ratios of the focal length by moving one optical unit. Moreover, to reduce aberrations, it is usually not a single negative lens that is used, but a combination of several. The idea of ​​placing this lens inside an extension ring for macro photography is also well known. This is how, for example, the MC double converter K-6V is designed. The focal length is approximately 113 mm. I calculated this value based on the thickness of the extension ring, equal to 56.5 mm. In the above diagram, this thickness corresponds to the difference SS ₀ =S ₀ , since the multiplicity is M=S/S ₀ =2 and M=f ₂ /(S ₀ +f ₂ ), where f ₂ is the focal length of the Barlow lens, which is a negative value , since the lens is concave.

However, if you remove the optical unit from this teleconverter, it will not be possible to install it between Canon EOS lenses and the device, since this design is designed for a larger working distance of medium format cameras. For a 2x teleconverter, its focal length must be greater than the working distance and less than two working lengths, otherwise we will either run into the lens frame or the body of the device. But the optical unit from a teleconverter for almost any 35mm SLR camera is suitable for our purposes. TK-2 teleconverters with M42 thread were produced in significant quantities and continue to be produced.

It was this that I initially planned to use as the basis for my design. However, a visit to the second-hand store showed that a more affordable option was the KIRON MC7 2x TELECONVERTER FOR OLYMPUS/OM, produced, you know, in Japan. Estimated focal length -82 mm. The frame was an extension ring 41 mm long with two OM bayonets and a diaphragm pusher, unfortunately, mounted on the optical block, and not on the ring frame, i.e. After removing the optical unit, it was no longer possible to use the frame as an extension ring with a pusher.

However, since I don’t have Olympus devices, and the mechanical pusher in the Canon system is replaced by wires, the frame with which I described in the previous article, all that remains is to make an intermediate ring with an M42 thread, screw the optical unit inside it, and, in turn, screw it onto two adapter rings connected by wire.

Since the teleconverter increases the focal length, I immediately took care of attaching it to a tripod, making an L-shaped support. The result is a teleconverter that can be used with Canon EOS lenses, mainly with manual focusing and electrical aperture control.

The thickness of the resulting converter is SS ₀ = 40 mm, this gives us a multiplicity of M = 1.97, which is confirmed by comparing the sizes in the photographs taken. Since the aperture diameter remained unchanged and the focal length doubled, the relative value also doubled. Since the aperture numbers differ by the square root, when installing the converter we lose two stops, and a lens with a relative aperture of 1/2.8 turns into a lens with a relative aperture of 1/5.6.

Without converter	With converter
The above images were taken in JPEG, and with the converter, chromatic aberration is clearly visible. If you take a file in a raw format and convert it in the UFRaw program, the AHD algorithm using the LensFun library to correct chromatic aberrations, the situation will improve noticeably. Operating principle of the teleconverter A teleconverter is a device that is designed to increase the focal length of a lens. In fact, the focal length of a lens cannot be changed, since it is a physical quantity that varies within the limits set by the lens designer. The teleconverter changes the way the lens works, so it is convenient to say that it changes the focal length. What is the purpose of the teleconverter? For example, if you have a lens with a maximum focal length of 200mm, and you desperately need a closer zoom, then there are two options: buy a new lens or put it on an old teleconverter. A teleconverter can double the focal length and can be mounted on any lens. Operating principle of the teleconverter The teleconverter enlarges the central part of the image, thereby increasing the focal length. It is installed between the camera and the lens. The converter itself has mounts that allow it to be easily attached to the lens and camera. Increase Most often, teleconverters provide magnification ratios of 1.4X, 2X, 3X . This means that the focal length will be increased by as many times as the converter. Usage If you use a 1.4x teleconverter with a 50-200mm lens, the lens will have a focal length of 70-280mm. Please note that as the focal length increases, the hole size will decrease. The aperture ratio, thus, the aperture ratio decreases several times. Teleconverter 1.4x - 2 times Teleconverter 2x - 4 times Teleconverter 3x - 8 times The loss of aperture can only be compensated by increasing the shutter speed. Thus, when shooting with a 2x teleconverter, we get a 2x zoom, but a 4x loss in aperture. This means the shutter speed needs to be increased 4x to reach normal exposure. For lenses with long focal lengths this is critical. You have to use a tripod and some tricks to release the shutter button to avoid the slightest movement. Types of teleconverters Teleconverters are divided into two types. Some support autofocus, while others do not. It's simple. Your lens will either gain autofocus capabilities when used with a teleconverter, or it won't. There are converters that need to be placed on the front of the lens. They are usually designed to widen the viewing angle. You can also attach several teleconverters in succession, resulting in an incredibly long focal length. Adviсe Good teleconverters cost a lot of money, but they allow you to use the autofocus of the lens. More often than not, it is better to buy an expensive telephoto lens than a cheap lens and a cheap converter. All teleconverters enhance the shortcomings of lenses. They negatively affect sharpness and aberrations. But at the same time, a teleconverter can rid the lens of distortion. Overview of the Soligor AF PRO tele-converter AFd 1.4x N/AFd Now, to understand what’s what, let’s look at the operation of the teleconverter using a real example. Next you can see cropped frames. The sharpness did not deteriorate too much. This teleconverter is not able to tell the camera that it has more than just a lens, so the camera operates as if it does not have a teleconverter. The converter lenses are slightly yellow. This changes the standard color rendering. Teleconverter Wikipedia open wikipedia design. Teleconverter , Teleextender ( Telenegative attachment ) is an additional optical system installed between the body of a camera, movie camera or video camera, and the shooting lens to increase its focal length [1]. On television, a teleconverter is called an afocal tele-attachment installed in front of the lens, and lenses of a similar purpose located behind it are called an extender. Some vari-photo lenses of professional video cameras are equipped with a built-in extender, which is installed in a special boss at the back of the frame and is introduced into the light stream by a switch [2]. Content Operating principle [edit | edit code ] For example, a 2x teleconverter enlarges the central 12x18mm image area to 24x36mm. Thus, using this teleconverter gives the effect of using a lens with twice the focal length. The negative side of using teleconverters is the reduction in the geometric aperture of the lens and the corresponding reduction in its relative apertures at all aperture values. Numerically, the relative aperture decreases by a multiple of the square of the converter's telemagnification. In practice, this means that using a 1.4 × converter reduces the relative aperture by half, and the exposure value (EV) by 1 stop, respectively, 2 × - by 2 stops, respectively. Another negative side of the teleconverter is its ability to increase aberrations of the lens itself. All other things being equal, a telephoto lens produces better image quality than a shorter focal length lens with a teleconverter. In reporting practice, a teleconverter allows you to reduce the number of portable lenses by using the same lens for shooting at different sizes. This is especially true for heavy telephoto lenses: for example, a 300 f/2.8 lens with a 2× teleconverter acquires parameters of 600 f/5.6, allowing you to vary the aperture and close-up depending on the situation. Two lenses with such aperture and focal lengths weigh significantly more than one “shorter” one in combination with a compact converter. Gains can be obtained even if a more powerful telephoto lens is replaced by a combination of a less telephoto lens with a teleconverter, since the weight and dimensions of high-aperture professional optics grow in proportion to the focal length. All this applies equally to primes and zoom lenses: in the latter case, it is easier to carry one long zoom lens than two. Consumer-grade telephoto lenses are much lighter and more compact, and their cost is comparable to the cost of a converter. The maximum aperture does not exceed f/4.5-5.6 and, when using a teleconverter, goes into the range of values ​​at which phase autofocus, especially on amateur cameras, becomes inoperative. In addition, most converters are designed for professional optics and are often incompatible with cheaper ones. Therefore, converters are less common among amateur photographers. The most common teleconverters are with a magnification of 1.4 × and 2 ×, 3-fold are less common. A controversial view on teleconverters Every photographer sooner or later thinks about purchasing a lens with a larger focal length than he currently has. And, since every person has the desire to have the best, soon, even if you have a 70-200 mm lens, you will want to add a 500 or even 600 mm to your arsenal. If you are looking for an affordable option to increase the focal length of your lens, then you should take a closer look at optical attachments such as teleconverters. They are not only cheaper, but much lighter and more compact than many bulky and heavy lenses. Their main advantage is that they increase the capabilities of lenses that you already have. However, they also have some disadvantages. Typically, using a teleconverter means a loss of sharpness, especially at the edges of the image, a decrease in lens aperture, and blur from even slight camera shake. General information A teleconverter, or extender as it is often called, is an optical attachment that is installed between the lens and the camera body and is used to increase the focal length of the lens. Most often there are two types of converters, with a multiplicity of 1.4x and a multiplicity of 2x. Due to their external similarity, teleconverters are often confused with extension rings. Unlike the first ones, extension rings are hollow and do not contain any optics inside. Their only purpose is to increase the distance between the camera itself and the lens. Rings are mainly used for closer focusing in macro photography. What are the benefits? It is quite obvious that the biggest advantage of using a teleconverter is the fact that it can increase the focal length by 1.4 times, 2 times or even 3 times. By using the 1.4x converter with a 200mm lens, you get a new maximum of 280mm. This is 40% more than you had before. And a 400mm lens with a 2x teleconverter will give you 800mm of focal length. To get this number, you need to multiply the focal length of the lens by the magnification factor of the teleconverter (400 × 2 = 800). Increasing the focal length allows you to take photographs that would otherwise be impossible due to the distance to the subject being too large. Thus, wildlife photographers get incredible photos of animals in their natural habitat, only while being at a decent distance from them. Many birds and animals are too shy or dangerous; photographing them at close range is often not possible. But by increasing the focal length, the hunter can move a considerable distance away from the shy object and still not lose in magnification. For sports photographers, this gives them the opportunity to capture the incredible moment of victory in great detail, even if they are on the other side of the stadium or standing to the side at a safe distance. Traveling is definitely a time when a teleconverter will come in handy. If you carry around another lens, which can be quite long and bulky, then this will not only cause you a lot of inconvenience, but also to some extent may limit your movement when shooting. And the lightweight, compact teleconverter is ideal for quickly moving from one location to another without feeling overwhelmed by equipment. Another plus is that buying a teleconverter will require a much smaller investment compared to the cost of purchasing another long lens. A teleconverter is an indispensable thing, especially when it comes to shooting moving objects, sporting events or hunting photography, in general, when there is no way to physically get closer to the subject. Sometimes the presence or absence of a teleconverter can make a big difference in whether you can capture an amazing shot or not. If the issue of sharpness is not as important for you as the fact of taking a particular picture, then undoubtedly a teleconverter is an ideal and quite affordable way to increase the focal length of your camera. What are the cons? Any teleconverter, regardless of its price, will have a certain impact on the quality of the pictures. By enlarging the image, it can not only enhance the effect of all your mistakes, but also highlight the optical aberrations of the lens used. The first disadvantage of using a teleconverter is that it limits the amount of light entering the camera. This means that a 1.4x teleconverter reduces the aperture by one stop, while a 2x teleconverter reduces the aperture by two stops. This may impose some limitations when photographing in low light conditions. If there is not enough light, then you should use a tripod and probably a slower shutter speed. However, if there is enough light, for example on a sunny day, then most likely you will not feel any restrictions. Since the maximum aperture of a lens will change, you will need to find a teleconverter that fits the lens. For example, it is better to use a 1.4x teleconverter with f/4 lenses, and a 2x teleconverter with f/2.8 lenses. Every time you increase the focal length, you will get even more camera shake. But using a tripod and increasing the shutter speed, with good lighting and a stable position, it is quite possible to achieve a relatively clear image. In addition, to completely eliminate any camera shake when mounted on a tripod, you must turn off the stabilizer on the lens. It should also be noted that teleconverters also affect autofocus performance. On some cameras, autofocus may not work at all and you will have to focus on the subject manually. Even if you have never used manual tuning, with a little practice you will quickly master this simple task. Manual focusing gives you more control over how you shoot, and you'll usually end up with the shots you want. Depending on the lens Each lens will "react" differently to a teleconverter partnership. Image quality will vary depending on whether you're using a super-telephoto lens, a mid-range zoom, or a wide-angle lens. With a long lens you can achieve the highest image quality - especially if it's a prime telephoto lens. For example, if you add a 1.4x teleconverter to a 500mm lens, it will have little effect on the quality of your images, whereas if you add the same teleconverter to a 100-400mm lens, you will only get average quality images. As for lenses like the 24-70 f/2.8 zoom, the teleconverter will most likely negatively affect the final image. If your lens is of high quality, then your teleconverter should match it. Otherwise, you are guaranteed to lose image quality. My advice: don't skimp on the teleconverter! After all, even the best teleconverter is much cheaper than a super-telephoto lens. When choosing a teleconverter, you should definitely check the compatibility of the teleconverter with the lens, since not all optics will work in pairs. Typically, each manufacturer indicates only their lens models in the list of compatible lenses. The image below is a good example of the quality you can achieve using a teleconverter with a super telephoto lens. The photo below was taken using a 100mm macro lens and a 2x teleconverter. Although there is a slight loss of sharpness, in principle, it is quite possible to achieve stunning images with a teleconverter. Testing extender 1.4x By looking at the following photos you will see the difference between the photos taken with and without the extender. These photos were taken with a Canon 5D MkII with a Canon EF f/2.8 70-200mm lens. When shooting, a 1.4x Canon EF extender was used. ISO values ​​for all images are 1000. 70-200mm at 200mm, f/3.5 70-200mm at 200mm with 1.4x extender (280mm), f/4.0 Now let's compare the sharpness of these images: Please note that images captured with the extender are slightly softer. If you can achieve the same quality without using an extender, I would recommend doing so. This way you can avoid loss of clarity. Remember that a lot also depends on the lens you use when shooting. Also, you may have noticed that the image taken with the extender is much darker. This shot perfectly shows how when using a 1.4x converter, the lens's aperture decreases and we lose one stop. Of course, all this can be corrected by changing the necessary settings. Magnifying the image Teleconverters enlarge the image, covering the central part of the camera sensor. But at the same time, the light that passes through the teleconverter is lost. Conclusion If a high-quality image at a distance is fundamentally important to you, then my advice to you is: give your preference to a long-focus lens, since with it, unlike a converter, the image will be clearer and more contrasty. However, you should not give up the converter either. It takes up minimal space in your bag, and will provide a lot of benefits. Thus, it is capable of turning a 50mm lens into a 100mm, 200mm, or even a 400mm lens. And if you add here a crop factor of 1.6-2 times, then you can get a fairly good range of focal lengths at a relatively low cost. Ultimately, your choice should depend on where you will be using your images. Will they be online only? Or are you going to print them in large sizes? Operating principle of the teleconverter Subscribe: Surely you have had moments when you wanted to bring your subject closer, but your lens did not allow it? An extra zoom can be useful in many situations, but for most of us, buying an additional lens is out of our budget - so what's a photographer to do? One solution to this problem is the ability to purchase a tele-converter for your lens. Teleconverters or extenders are cheaper than a new lens and can increase the focal length of your lens by 1.4 to 2 times. Let's look at all the pros and cons of teleconverters. Keep in mind that extenders do not work with all lenses. You should check with the manufacturer before purchasing to see if you have compatible lenses. Pros of Teleconverters Cost - Compared to, say, the cost of buying a 400mm lens, a teleconverter is a much more economical option. Weight - lenses with long focal lengths are quite bulky and heavy. Minimum Focus Distance - Using an extender means you can maintain the minimum focusing length of your lens. This can be handy when you don't have a macro lens handy and want to capture a close-up subject very closely. Cons of Teleconverters Using teleconverters means that less light enters them, which means the maximum aperture is reduced. When using a 1.4x converter this means you will lose one aperture stop, and when using a 2x converter you will lose two aperture stops. Camera shake – As your lens increases in focal length, any movement of your camera becomes more noticeable. Using a teleconverter magnifies both your subject and any movement in your camera, so you should think carefully about how to reduce it by increasing your shutter speed or using a tripod, monopod, or other camera stabilization method. Focus Speed ​​– Another consideration with teleconverters is that they slow down your camera's focusing speed. This will vary from lens to lens, but is especially an issue in low light. Some low-quality DSLRs will not be able to autofocus at all with some teleconverters at certain aperture settings (or at all), so check your camera's compatibility before purchasing. To get around slow focusing, switch to manual focus mode and learn how to use it - you'll be surprised how quickly you can do it yourself - it's a useful skill. Image Degradation - Extenders not only multiply the focal length, but also any aberrations of the lens you pair it with. On many lenses, image quality deteriorates noticeably, especially with longer extenders (x2). Sharpness and contrast are the first to suffer, especially when shooting in the light (where flare and ghosting can be quite noticeable). Using the best quality lenses will help minimize this degradation. Overall verdict Using teleconverters is a more affordable way to increase focal length than buying a longer lens, but it can result in reduced image quality and camera performance unless you are working with a high-quality lens in sufficient lighting. When using extenders, try not to use them at the maximum aperture that your camera allows, but stop it at least one stop and the results will be quite acceptable. Also keep in mind that longer focal lengths will leave you with fewer options to change the depth of field, so your focusing needs to be precise. Find out more in our Photographic equipment section Save to: Operating principle of the teleconverter Link to main publication For any suggestions regarding the site: [email protected]