Photographing a distant object with a camera lens. Learn more about telephoto lenses. Telephoto lenses for Canon. Increasing the focal length of the lens
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628. What exposure is needed when photographing a drawing with a linear increase V \\, if when photographing with an increase in V2, the exposure is equal to t2?
629. Frosted glass is installed in the focal plane of the positive lens. It turned out that the blurring of image details of objects located at a distance of a \u003d 5 m from the lens was d \u003d 0.2 mm. Determine the lens aperture if its focal length F \u003d IO cm.
Note. Aperture lens is called the square of the ratio of the lens diameter to its focal length.
630. A camera, the lens of which has a focal length of F \u003d 20 cm, is aimed at an object located at a distance of fli \u003d 4 m. To what diameter should the lens be diaphragmed so that the blur of an image of objects at a distance a2 \u003d 5 m from the camera does not exceed 0.2 mm?
631. When photographing a distant point source in a photograph, due to the low quality of the lens and the used photographic material, a light circle with a diameter of d \u003d 0.1 mm is obtained. From what maximum distance can two point sources be photographed under the same conditions, located at a distance of I \u003d 1 cm from each other, so that at
127photographs have their images overlapped yet? Lens focal length F \u003d 5 cm.
632. In a microscope, the main focal length of the objective is Fi \u003d 5.4 mm, and the eyepiece is F2 \u003d 2 cm. The object is located from the objective at a distance of ax \u003d 5.6 mm. Determine the linear magnification of the microscope for a normal eye and the length of the microscope (the distance between the objective and the eyepiece), assuming that the eye is accommodated at the best vision distance d \u003d 25 cm.
633. The objective of the telescope has a focal length Fі \u003d 30 cm, and the eyepiece has a focal length F2 \u003d 4 cm. The tube is set to infinity *). Where should the diaphragm be placed so that the field of view is sharply limited? What is the angle of the field of view if the diaphragm is 12 mm in diameter? What is the angular increase of the pipe?
Note. Angular magnification is the ratio of the tangents of the angles formed by the outgoing and incoming beams with the optical axis.
634. A diffusing lens with a focal length Fi \u003d -15 cm at a distance of U \u003d 85 cm from the source is placed between the light source and the telescope. Where in the gap between the source and the diffusing lens should a converging lens with a focal length F2 \u003d 16 cm be placed so that the light source can be seen sharply into the tube set at infinity? At which of the possible positions of the lens will the image in the tube have the largest angular dimensions?
635. The telescope lens has a focal length Fi \u003d 25 cm and a diameter of 5 cm, and the eyepiece has a focal length F2 \u003d 5 cm. The tube is set to infinity. If a frosted glass is placed behind the eyepiece, then at some of its position the illuminated circle on the frosted glass has the smallest dimensions and sharply limited edges. What is the distance from the frosted glass to the eyepiece and what is the diameter of the circle?
*) The text of this and a number of subsequent problems does not contain instructions regarding the accommodation of the observer's eye. In such cases, it is recommended to solve problems under the assumption that the eye is accommodated to infinity (see the note to the solution of this problem). ...
128636. The telescope with the focal length of the lens F \u003d 50 cm is set to infinity. How far should the eyepiece of the tube be moved in order to clearly see objects at a distance of a \u003d 50 m?
637. By moving the eyepiece, the telescope can focus on objects located at a distance from Cil \u003d 2 m to a2 \u003d 10 m. What lens must be attached to the objective so that the telescope can be adjusted to infinity? Where will the nearest focus point be?
638. In front of the Kepler telescope objective (with a collecting lens as an eyepiece), an object is placed at a distance a< Fi. Отношение фокусных расстояний объектива и окуляра FiIF2=IO. Труба установлена на бесконечность. Найти линейное увеличение V = у/х (л;-размер предмета, у- размер изображения). Определить характер изображения.
639. Before the objective of Galileo's telescope (with a diffusing lens as an eyepiece) an object is placed at a distance a\u003e Fi. The ratio of the focal lengths of the objective to the eyepiece FJF2 \u003d -10. The pipe is pointed at infinity. Find the linear magnification V \u003d y / x, where X is the size of the object, y is the size of the image. Determine the nature of the image.
640. The telescope has a lens focal length Fi \u003d 50 cm and an eyepiece focal length F2 \u003d 10 cm. What is the angle at which two distant objects are visible through the tube if this angle is 30 "when observing with the naked eye? The tube is set to infinity.
641. The objective and the eyepiece of Galileo's telescope have focal lengths equal to F \u003d 57 cm and F2 \u003d -4 cm, respectively. The tube is aimed at the Sun. A white screen is located at a distance b \u003d 12 cm from the eyepiece. At what distance L between the lens and the eyepiece on the screen, a clear image of the Sun will be obtained. What will be the diameter D of this image if the angular size of the Sun is a \u003d 30 "?
Thin lens formula
2. When photographing a very distant object with a camera, the objective of which is a converging lens with a focal length f, the plane of the photographic film should be at a distance from the lens A - Between the lens and the focus (f) B - Between f and 2f C - Equal f D - Equal 2f
3. Using a lens, an inverted image of a candle flame was obtained on the screen. How will the image be resized if part of the lens is obscured by a sheet of paper? A - part of the image will disappear B - the size of the image will not change C - the size will increase D - the size will decrease
4. An object located near the focus of a thin collecting lens is moved to a double focus (see Fig.). His image in this case ... A - approaches the double focus of the lens B - moves away from the double focus of the lens C - moves away from the focus of the lens D - approaches close to the focus of the lens
Right!!! Hooray! Five points!!!
When compiling the presentation, the following materials were used: 1.CD "Physics Media Library", Cyril and Methodius Virtual School 2.CD "Preparation for the Unified State Exam. Physics ", PHYSICON For 4 years now, for a survey in physics lessons, I have been using the game" Who wants to become an excellent student in physics? " (idea borrowed from a TV game). The game takes 3-4 minutes and makes the lesson very lively. The rules of the game: a student at the blackboard (more precisely, at the projector screen) receives 6 questions and has the right to take two hints: ask the computer to remove two incorrect answers and get help from the class (so all students are on their toes!) Each wrong answer lowers the mark by a point.
Photographic optics was known long before the invention of photography and was used by artists as an auxiliary tool for accurately depicting landscapes. The optical design of two converging lenses was first described by Kepler in 1611, but was forgotten and reinvented by Barlow in 1834, and in 1891 such a lens was used by Dallmeyer for photographic purposes. It should be noted that Kepler did not embody his design "in glass", but his theoretical research had a significant impact on later developments.
Historically, the main applications of telephoto lenses have been close-up photography and portrait photography. In the latter case, long-focus optics provide minimal distortion of the proportions of the face and good separation of it from the background, which, being out of focus, is blurred. These two directions are relevant in photography today. In addition, telephoto lenses allow for many other interesting types of photography.
The largest telephoto lens for civilian use to date, designed and built by Carl Zeiss. It has a focal length of 1700 mm, a maximum relative aperture (aperture) of F / 4 and a mass of 256 kg (photo 1). This lens is a one-of-a-kind product commissioned by the amateur long-distance wildlife photography with very high demands on image quality.
Optical schemes of telephoto lenses
The simplest lens design, which is a single long-focus lens, has several disadvantages. The most significant of them are the low image quality and very large dimensions of the structure. The length of such a lens when focusing at infinity is equal to its focal length. Therefore, a different optical design is currently used, called a telephoto lens. In the simplest case, a telephoto lens consists of one converging and one diffusing lens, however, in order to reduce aberrations, they are usually replaced by groups of lenses made of glass with different optical properties (Fig. A). Modern telephoto lenses usually use additional lens groups to further improve image quality and provide additional functions such as image stabilization, while the overall design concept remains the same.
There is usually a diaphragm between the lens groups. This device limits the cross section of the light beam and is used to change the amount of light passing through the lens and the depth of field. The blur shape in the out-of-focus area is an image of the aperture opening.
Telephoto lenses lengthen rapidly with increasing focal length. To ensure sufficient aperture, the lens has to be made with a large diameter. As a result, the weight and price of the lens increases. The problem of creating compact ultra-long-focus objectives has been successfully solved using a mirror-lens optical scheme reminiscent of a classical telescope (Fig. B). In such a scheme, the diaphragm is absent (its optical role is usually played by the frame of the front element), the lens has a fixed aperture ratio and relative aperture, and image blur outside the sharpness zone has a characteristic annular shape.
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Mechanical properties of telephoto lenses
As mentioned, telephoto lenses are usually quite long. To obtain acceptable values \u200b\u200bof the relative aperture, which affects the amount of light passing through the optical system, it is necessary to use lenses of large diameter. All this leads to the fact that a quality telephoto lens cannot be made light and compact. With small sizes of light-sensitive material (for example, in compact digital cameras) this limitation is insignificant; however, an increase in the required image size leads to a proportional increase in the linear dimensions of the optics. A moderate telephoto lens with a true focal length of 200mm and an aperture of f / 2.8 is no longer easy to hold in the hand for a long time: in such a situation, it is better to use a tripod or monopod.
In addition, the small angle of view of a telephoto lens results in a very small rotation of the optical system leading to a significant shift in the image. If this shift occurs during exposure, the photo is blurry. The empirical formula, correct for most cases, states that when shooting handheld, the "safe" (in terms of image blur) shutter speed (in seconds) should be numerically no more than the reciprocal of the equivalent focal length (in millimeters). Especially "long" lenses prevent this condition from being met even in bright scene illumination. To remedy the situation, two fundamentally different approaches are used. One of them is to fix the optical system in space as reliably as possible and prevent it from moving during shooting. For this, tripods or monopods are used. Less often, more expensive and bulky gyroscopic platforms are used, which move freely in space, but precisely retain the initially specified orientation. The second method, called optical stabilization, consists in introducing a special moving element into the optical system to compensate for the image shift as a result of camera shake. This element can be either one of the objective lenses, or a platform on which the light sensor of a digital camera is mounted.
Very large lenses weigh much more than the camera they are mounted on. Therefore, they have a special mount, usually in the form of a clamp with a platform, for mounting the system on a tripod. Sometimes the device is designed with a handle for carrying it. The already mentioned giant Carl Zeiss Apo Sonnar T * 4/1700, due to its weight and dimensions, is intended for installation on a special platform mounted in the body of a car. In such extreme cases, it is more logical to talk about installing the camera on the lens, and not vice versa.
The focusing of fast long-focus lenses is associated with the movement of massive lenses. This greatly reduces the speed and accuracy of automatic focusing and increases power consumption. One of the most important areas of modern research is to improve these parameters. Partly for the same reason, the minimum focusing distance increases rapidly with increasing focal length. By introducing this limitation, it is possible to shorten the course of the components in the focusing process, and therefore to shorten the focusing time. Some lenses have a switch that allows you to choose a range of focusing distances: full - for shooting close objects, or short - to speed up the process.
To reduce the length and weight of the lenses, they use expensive optical glass with an extremely high refractive index. Some modern developments use diffractive optics for the same purpose.
Increasing the focal length of the lens
It happens that the focal length of the lens is too short for solving a specific photographic task. In some cases, replacing the lens with a longer focal length is impossible (for example, when using a compact camera with non-interchangeable optics) or undesirable (usually super telephoto lenses are quite expensive). Optical devices called teleconverters come to the rescue. They can be divided into two large classes: placed between the lens and the camera in the manner of extension rings and installed in front of the front lens of the objective.
For increasing the focal length of the optical system with such methods, you have to pay with a decrease in aperture. 1.4x teleconverter reduces the aperture ratio by one stop, 2x - by two. That is, for example, when using an F / 2.8 lens and a 2x teleconverter, a system with an F / 5.6 aperture ratio is obtained. Not too much, but perfectly acceptable. Image quality usually suffers slightly when using teleconverters from the same manufacturer that made the lens, but cheaper third-party products should be purchased with caution.
Image features
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Photographing any object is geometrically represented by its image on a plane in the central projection. This is true with any distortion corrected lens. All existing long-focus optics have this property, so we will not consider other cases.
The size of an object that covers the entire area of \u200b\u200bthe frame depends on the size of the frame, the focal length of the lens, and the distance from the camera to the object. By reducing the area of \u200b\u200bthe frame, you can achieve upscaling when printing an image while maintaining the same paper size. Therefore, the focal length of a lens by itself cannot be a measure of its wide angle. For example, a lens with a focal length of 50 mm would be normal for a 135 type film with a 24x36 mm aspect ratio, a wide-angle for a medium format 60x45 mm, and a super telephoto camera for a digital camera with an 8x6 mm sensor size. To simplify the calculations, the concept of equivalent focal length was introduced, which is defined as the true focal length of a lens that has the same angle of view with a frame diagonal of 43 mm, which corresponds to the most widely used type 135 film.
Lenses with an equivalent focal length of about 40-50 mm are called normal because they give an image similar to that seen with the naked eye (in both cases, the spatial relationships of objects will be visually the same). Shorter focus optics are called wide angle. In this article, we are looking at lenses with an equivalent focal length that is significantly longer than normal.
As teleoptics, you can use versatile zoom lenses, which are often installed in compact cameras with non-interchangeable optics. Image geometry is independent of lens design and is determined only by its equivalent focal length.
As strange as it may sound, the spatial relationships between the parts of the subject's image do not depend on the focal length of the lens with which the shooting was made. They are determined only by the distance from the camera to the subject. This statement is easy to prove using elementary information from geometry; we propose to solve this problem for curious readers on their own.
Note that the invariability of spatial relationships implies the "geometric" equivalence of digital and optical zoom. But in practice, the use of digital zoom leads to a decrease in the maximum image resolution. This happens because the digital zoom “cuts out” a smaller fragment from the frame, which means that it uses only a part of the light-sensitive elements of the matrix. You can achieve the exact same effect by cropping a picture taken without digital zoom in the camera.
Let's talk about telephoto lenses
Warning - the article is based on personal experience only. The main focus is on the Canon technique I have worked with during my photographic experience.
What is a telephoto lens for?
Probably, at least half of the owners of DSLRs with a standard zoom lens want to buy a telephoto lens. When asked "why do you need a telephoto lens?"
most often one hears an answer that is difficult to argue with - "to bring everything closer!" :) As a rule, a telephoto lens is really used for shooting objects that cannot be approached - from banal water lilies and houses "on the other side" to professional photography, sports photography, shooting airplanes and so on. Telephoto lenses are also often used for portraits due to their ability to strongly blur the background. Some telephoto cameras allow you to shoot good macro. In other words, the range of tasks that a telephoto lens can solve is quite wide.
This article covers the basics when choosing, buying and using a telephoto lens.
How to choose a telephoto lens
Each manufacturer of photographic equipment, as a rule, has a huge number of long-focus lenses. If we consider Canon, then at least a dozen models come to mind (we don't take fixes into account yet)!
- Canon EF-S 55-250mm f / 4-5.6 IS
- Canon EF 70-200mm f / 2.8 USM L
- Canon EF 70-200mm f / 2.8 USM L IS
- Canon EF 70-200mm f / 4 USM L IS
- Canon EF 70-200mm f / 4 USM L
- Canon EF 70-300mm f / 4-5.6 USM IS
- Canon EF 70-300mm f / 4-5.6 USM L IS
- Canon EF 100-300mm f / 5.6 L
- Canon EF 100-400mm f / 4.5-5.6 USM L IS
The situation is similar for other manufacturers. All this variety is complemented by a large number of telephoto models from Sigma, Tamron. Telephoto lenses can cost anywhere from a few hundred to several thousand dollars! How do you make sense of all this variety and choose a telephoto lens with an optimal ratio of price, functionality and image quality?
First of all, let's do a little freestyle telephoto classification.
By focal length
Like all optics, telephoto lenses are divided into zooms and fixes. A zoom lens has the ability to change the focal length within certain limits, thus changing the scale of shooting an object from medium to very large (wide-angle lenses give a small scale, they were discussed earlier).
Telephoto lenses with a fixed focal length do not have such an opportunity, so you have to run around to frame with them. Moreover, taking into account their very small viewing angle, you will have to run over very long distances, and sometimes even climb mountain slopes, ladders, ladders, trees - depending on what we are going to shoot. The use of long-focus fixes is mainly the lot of photo hunters, astrophotographers, sports photographers. As a rule, special platforms are used for shooting, booths, the location of which is "adjusted" so that the scene of action is clearly visible and the distance to the shooting objects is optimal for using a given focal length.
Sports photographers with telephoto fixes
In everyday use, zoom lenses are much more practical. In most cases, they have the worst aperture and image clarity, although there are also very sharp and beautifully drawing zooms - in this case we are talking about professional "moderate" 70-200mm telephoto lenses.
A lens simulator will help to give a more clear idea of \u200b\u200bhow the "degree of approximation" is related to the focal length:
See how the field of view of a lens changes with focal length and when used on a full frame sensor (FX) and at a 1.5 crop (DX).
By aperture
The aperture ratio characterizes the maximum light transmission of the lens. The faster the lens, the more light gets to the matrix (with the aperture fully open) and the faster the shutter speed is required. Another well-known regularity is that the higher the aperture ratio, the greater the range you can change the depth of field. This is true for portraits, where lenses are highly valued for their strong and beautiful background blur.
High-aperture long-focus optics allows you to bring to life a large number of creative ideas. As a rule, these are very expensive professional grade lenses. One of the elements of prestige for every manufacturer is "moderate" telephoto lenses with a focal length range of 70-200mm and a constant f / 2.8 aperture. These are professional zoom lenses "sharpened" for portrait photography. They, as a rule, give excellent image quality - in the field of sharpness, the detail is huge, while the background is blurred very strongly and beautifully. Contrast, color rendering, light resistance are also at a very high level. Lenses 70-200mm f / 2.8 are very popular among wedding photographers, allowing you to simultaneously solve the tasks of reportage and portrait photography. Lenses of 70-200 mm also have "lightweight" versions - with a constant aperture of 4. They are noticeably cheaper and more compact than their "older brothers", but they also have less capabilities, although, in fact, these optics are very good.
The aperture of most amateur telephoto lenses is quite low - at the short end of f / 4, at the long end - f / 5.6 and even less. This imposes some restrictions on the use of such lenses in artistic portrait photography (which is most often carried out in the range of up to 135-150 mm) and shooting fast-moving objects - due to the small amount of light entering the matrix, you have to raise the sensitivity a lot for shooting with a short shutter speed. ISO.
If you look closely, among professional telephoto lenses, sometimes there are not very fast ones! Here's an example:
- Canon EF 70-300mm f / 4-5.6 USM IS (costs about 20,000 rubles)
- Canon EF 70-300mm f / 4-5.6 USM L IS (costs about 45,000 rubles)
It seems that the differences are only in one letter, but "elka" costs more than 2 times more. What's the catch?
In fact, these lenses look quite similar to each other (regular 70-300 black, elka white and slightly larger in diameter). The difference is in the filling. Lenses have different optical design and use lenses of different classes. As a result, an inexpensive "simple" 70-300 has an acceptable picture quality only for 2/3 of its range (somewhere up to 200 mm), then there is a noticeable decrease in sharpness, chromatic aberrations appear. "Elka" gives a brighter, juicier and sharper picture over the entire range of focal lengths.
By the presence / absence of stabilization
As you probably know, Image Stabilizer helps to compensate for camera movement caused by shake of the photographer's hand, thus allowing you to shoot at slower shutter speeds and still get clear shots. Nowadays stabilizers are installed in almost all lenses, but stabilization is most relevant in long-focus optics, that is, in telephoto lenses.
There is such a rule - to get guaranteed sharp pictures, you need to shoot with a shutter speed no longer than 1 divided by the focal length (in film equivalent). That is, if we have a focal length of 50 mm, then the "safe" shutter speed will be 1/50 of a second (and shorter). If a telephoto lens has a focal length of 300 mm, then the "safe" shutter speed will be 1/300 second on a full frame and about 1/460 second on a "cropped" camera (in terms of 1.6 crop, 300 mm turns into 460 mm).
It follows from this that a 300 mm telephoto lens will only be able to shoot handheld on a bright sunny day! If the shutter speed turns out to be longer than the safe one, there are ways out - to open the aperture wider (often sacrificing detail), raise the ISO (this increases the noise level), or use a tripod (this reduces the photographer's mobility).
And here stabilization comes to the rescue - the included stabilizer is able to increase the safe shutter speed by 2-3 times. That is, instead of 1/300 of a second, the "safe" shutter speed for 300mm will be 1/100 of a second (1/160 sec on a crop). Agree, the stabilizer gives a serious advantage and allows in most cases to abandon the use of a tripod and shoot at low ISO sensitivity not only in sunny but also in cloudy weather, sometimes even in the evening.
Thus, it can be concluded that the telephoto lens is extremely useful for image stabilization. However, in fairness it should be noted that the stabilizer is useful only when shooting immobile objects (for example, a landscape). If you are going to shoot moving objects, for example, athletes, stabilization will not help you - to "freeze" the movement, you need to reduce the shutter speed by opening the aperture and / or raising the ISO sensitivity.
What you need to know when buying an inexpensive telephoto lens?
The main disadvantages of most budget telephoto lenses are low aperture, a noticeable decrease in image quality with increasing focal length, chromatic aberration, vignetting at open aperture. Some especially cheap models do not have image stabilization - such lenses are included in the special offers of stores and are "sold" along with budget DSLRs as a bonus (of course, not free). Thus, stores get rid of stale illiquid goods. Before you "bite" on such a proposal, think about what you will photograph with this lens?
Portrait
Yes, compared to a whale lens, this lens will blur the background better. Below is a portrait taken with a Canon EF 75-300mm f4-5.6 IS USM telephoto lens (75mm f / 4 Canon EOS 300D)
As you can see, there is blur, but not very strong. To enhance it, you need to increase the focal length to about 200 mm. The following example is a portrait taken with a Canon EF 100-400mm f4-5.6L IS USM telephoto lens (focal length 210mm, f / 5.6, Canon EOS 5D)
It's better, but I had to shoot from a very long distance (about 10 meters), which is not always convenient.
But if you try to shoot portraits with a high-aperture prime, even if it is inexpensive and not so long-focal, for example, 50mm f / 1.8, you will probably completely lose the desire to continue shooting portraits with a budget telephoto lens and immediately there will be a desire to save up for a good "portrait", for example, 50mm f / 1.4 (better for crop) or 85mm f / 1.4 (better for full frame). They cost about the same as a budget telephoto lens, sometimes even cheaper.
The last photo was taken on a Canon EOS 5D with a Samyang 85mm f / 1.4 lens at full aperture. You can see how much blur can be achieved with a fast "portrait" fix. Moreover, the shooting distance in this case did not exceed 3 meters.
Landscape
Although landscape photography is not the primary function of a telephoto lens, it can sometimes be successfully used to capture interesting pieces of a landscape. You can judge the quality of a cheap telephoto lens when shooting a landscape from these two photos:
Focal length 220 mm
Focal length 300 mm
The pictures were taken with a 6-megapixel Canon EOS 300D and a Canon EF 75-300mm f / 4-5.6 IS USM lens back in 2005. We see that at 220 mm the quality can be called tolerable at a stretch, but at 300 mm there is no sharpness! Nevertheless, I recently saw in the store a "double kit" - an 18-megapixel Canon EOS 600D with a kit lens of 18-55 mm and a Canon 75-300mm lens (you have already seen the photos from it), and the version without stabilizer! Is it worth throwing out small, but still money for such optics?
Someone will rightly argue that the new telephoto lenses have improved picture clarity. Yes, but do not forget that at the same time the resolution of the matrices has increased many times over, therefore, even if the situation as a whole has improved, it will not be radical - 100% of the crop of photos will be about the same. Budget telephoto lenses on the long end are not capable of providing a really high quality picture.
Photo hunting
Due to the low resolution at the long end, photographs of animals and birds will only be suitable for small format printing or publication on the Internet. Due to the low aperture, you will have to significantly increase the ISO in order to photograph animals and birds in motion - this will cause increased noise in the images. It will quickly become clear that 250-300 mm is too small for photographing animals in their natural habitat, the maximum of whom you can take more or less close-ups are animals accustomed to people (cats, dogs, pigeons, etc.) ). Wild animals with such a lens can only be photographed in the zoo (through the bars and glass walls of the enclosures).
Travel photography
For these purposes, "travel-zoom" is much more convenient - a lens with a focal length range from wide-angle to moderate telephoto. The most popular crop zoom travel zooms are Canon 18-135mm, Nikon 18-105mm. Having two lenses - a standard zoom and a telephoto lens, you will inevitably face two difficulties - the dimensions and weight of the kit (two lenses are larger and heavier than one), as well as the need to swap these lenses (risking dropping something or picking up dust on the matrix). From my own experience, I can say that during excursions it is quite rare to have the opportunity to take pictures leisurely - even if the guide gives you free time, there are a lot of people who want to take pictures and you will have to act quickly. In this respect, it is preferable to have one versatile lens rather than two for different purposes. The picture quality of the "travel-zooms" is quite good, they often surpass both the kit lens and the budget telephoto lens.
If you strain, you can still find a bunch of reasons to dissuade you from buying a cheap telephoto. But if the desire to buy has still not disappeared, then I will give some recommendations - how not to make a mistake with the purchase and how to enjoy the shooting?
1. The main recommendation - if the lens is not fast, it is highly desirable to have a stabilizer. Image stabilization will significantly reduce the percentage of rejected images due to shake, and will also make it possible to cover the aperture up to 8-11 - it is at these values \u200b\u200bthat the best sharpness is achieved.
2. Do not mess with "super zooms" - 18-200mm, 28-300mm, 18-270mm, etc. They have a useless aperture at the long end, the image clarity of such lenses can be an order of magnitude lower than, even, of a whale 18-55 mm.
3. Be sure to check the lens for front / back focus.
Which lens to buy - "cropped" or "full frame"?
If you have a "cropped" camera and you do not plan to switch to full frame in the foreseeable future, I personally do not see much sense in purchasing a "full-frame" 70-300 mm lens - it costs one and a half times more, at least, and the quality is comparable to "cropped" lenses of the 55-250 mm family.
Let me remind you that budget telephoto cameras have only 2/3 of the "working" range, then there is a noticeable decrease in definition. At the same time, the difference in "effective" focal lengths between 55-250 and 70-300 disappears altogether.
The lens 55-250 is not devoid of mechanical flaws - it does not have dust protection, with a telescopic design this will inevitably cause dust to enter and settle on the lenses. But for such a price, this is a very good purchase, especially if it is included in the so-called "double kit" - then its price turns out to be generally ridiculous.
There is also a very interesting option - Canon EF 70-200mm f / 4 L USM... Its cost is about 40 thousand rubles (used can be found cheaper). Despite the fact that this cheapest version of the lens does not have a stabilizer, its picture quality is noticeably better than that of the telephoto lenses mentioned above. For some, this will be a strong argument - when using a tripod, this lens will allow the result simply unattainable for budget optics.
The lens has an extremely robust design with internal focusing and internal zooming to prevent moisture and dust from entering the lens. Disadvantages - rather large dimensions and considerable weight. There is a version of the lens with a stabilizer, but it costs 1.5 times the basic version.
Canon EF 70-200mm f / 4 L USM IS
Third-party budget telephoto lenses - should you contact?
The most popular third-party manufacturers are Sigma and Tamron. As a rule, their lenses are cheaper than the original ones, but they are often not worse in their characteristics and provide comparable or even better image quality. But there are also pitfalls. The main one is the greater likelihood of running into a low-quality copy. If you are inclined to buy a Sigma, Tamron telephoto lens, I recommend not to take the first lens that comes across, but to test several copies and choose the best one.
How to choose the best one?
There are two ways - to take photos with all test lenses, and then look on a large screen (for example, on a laptop taken to the store) to choose the one with the best picture quality. The option is reliable, but not always acceptable - it is not always possible to use a laptop.
The second way is to put the camera on a tripod, fix its settings and put all the lenses from the test set on it in order, shoot the same thing and look at file size! The larger it is, the better the detail in the photo. This method allows you to quickly select the sharpest instance. But, I repeat, absolutely equal conditions must be created for all lenses. Best suited for photography are variegated objects that completely fall into the depth of field, for example, a page with text, a shop window, a poster on the wall.
How to test a lens upon purchase, read my essays.
It might be helpful to read:
- Presentation "Strong and weak electrolytes" presentation of a lesson for an interactive whiteboard in chemistry (grade 9) on the topic Presentation on the use of electrolytes in medicine;
- Presentation on the topic: "Acids - as electrolytes" Presentation on the use of electrolytes in medicine;
- Presentation vladimir dal presentation for a reading lesson on the topic Literary presentation for grade 4;
- More about telephoto lenses;
- Creativity of Korney Ivanovich Chukovsky presentation for a reading lesson (grade 2) on the topic;
- Presentation on the topic "Biography of Paustovsky. Presentation on the topic of Paustovsky biography;
- Migratory and wintering birds presentation Migratory and wintering birds presentation for children;
- Traumatic brain injury Presentation on the topic of closed traumatic brain injury;