What is a camera lens? First of all, it is the soul of the camera. The soul consists of several lenses located in the body (the latter is also called the frame), and the objective of the lens is to project the picture of the real world you have seen onto the surface of the matrix (or film). At the moment of pressing the button, the optics transmits light and draws an image of the required size on the matrix. Light painting, not otherwise. In this article, I will try to cover all about camera lenses for beginners.
Camera lenses are known to be characterized by focal length and aperture ratio. In fact, lenses can have many characteristics: bayonet type, lens coating, resolution, automatic (or manual) focusing, they can transmit data to the camera, have dust and moisture protection or not. Almost all modern lenses are equipped with automation, many are packed with electronics, various micromotors, and an image stabilizer is also built into Canon and Nikon optics.
In addition, lenses can be permanently built into the camera (as in compacts), or they can be in the form of a separate device that is placed on a camera with interchangeable optics (for example, a SLR camera.) Such lenses expand your photography capabilities almost unlimitedly, and to the same extent they empty the wallet. 😜😜😜 Interchangeable lenses can be sold separately, or they can come with the camera. So let’s also figure out what a camera lens is, what is its structure and main characteristics.
To some extent, the camera lens device mimics the human eye. The main task of lens is to focus the light flux coming from various objects and to form a focal point on the light-sensitive material. Lenses play the main role in the optical design. These are glass plates of a round shape, which are given a certain curvature by polishing and grinding. All photographic lenses are divided into the following groups:
Depending on the direction of curvature, lenses can be converging and diffusing. The first two groups are collective. They focus the light flux into one point. Thus, one convex photographic lens can play the role of the optics of a camera. A photographic lens that has a single lens device is called a meniscus. Such a simple optical system allows obtaining an image of an object on a light-sensitive material, but it will be of low quality. The fact is that the curvature of the optical glass changes from the periphery to the center, so the image of the object will be greatly distorted at the edges of the frame. Distortions of the picture are called aberrations and can be chromatic (color) and geometric.
In the first case, a colored border appears around the objects, disrupting the normal perception of the photograph.
Geometric distortions are associated with the fact that rays passing through the central and peripheral parts of the photo lens are refracted at different angles. This entails curvature of straight lines or distortion, which can be in the shape of a barrel or pillow. To get rid of all types of aberrations, additional lenses are installed in the optical set of the camera.
Types of Optical Systems
In the process of development of practical optics, the optical design of lenses changed, and their design became more and more complex. After a meniscus consisting of a single photo lens, the following variations were developed:
“Achromat” is a glued pair of two photo lenses. One of them is convex, the other is concave. In the photo lens of such a device, there are no chromatic distortions and geometric distortions are partially corrected. They are used on mobile phones and smartphones.
A more complex version – “aplanat or aplanatic”, consists of two achromats. It resolves most of the problems associated with chromatic distortion, distortion and partially corrects astigmatism.
Optics in which almost all aberrations are almost eliminated is called “anastigmat”.
Modern Lens Design
The optics of modern cameras belongs to the anastigmatic and has a complex structure. It consists of several lenses of various curvatures and some technical devices located inside the optical system. The number of photo lenses can be up to 15-20. They are usually grouped into several blocks. To increase the contrast of the image by damping glare, an ultra-thin coating of rare metal oxides is applied to the lenses. Usually lanthanum and its compounds are used for this purpose. This process is called enlightenment. In general, the optical system consists of the following units:
- Lens blocks;
- Diaphragm mechanism;
- Stabilization system;
- Fastening device;
Lenses for the most expensive representatives are polished from a transparent type of fluorspar and have the lowest refractive index, which makes them suitable for use in super telephoto lenses. The distance between lenses and lens units is calculated with high precision. These values determine the characteristics of the optics of the camera. Therefore, professional lenses have a rigid body made from durable and lightweight alloys. Plastic structures are cheaper, but less reliable and may develop backlash over time.
Mechanical Components in Lens Construction
Let’s consider the main mechanical components in the optical system.
The focusing lens plays an important role in the lens design. Unlike other optical elements, which are rigidly mounted on seats, the focusing lens can move within the system. It is designed for focusing.
With older cameras, this process was done manually. For this, there was a corrugated ring on the photo lens, on which marks of the distance to the object being shot were applied. On simple models without range finders, the distance was set “by eye” on a scale, where there were marks from 0.8 m to infinity (∞). The optical rangefinder reduced the likelihood of error, since the photographer, due to the absence of “blurring” of the image in the viewfinder, precisely chose the desired distance.
The device of modern systems includes both an automatic focusing system using a miniature electric motor and the ability to manually set the focus point. The autofocusing algorithm may differ slightly depending on the camera manufacturer, but the results are usually the same.
The diaphragm is a mechanical device located inside the lens between the lens groups. These are several thin metal plates, usually 5-9, of a certain shape, which are mounted on a rotating ring. The main task of the diaphragm is to limit the amount of light passing through the optics. At maximum aperture, the lens is fully open. If you need to reduce the amount of light, then rotating the diaphragm ring selects a higher numerical value represented by a fraction, for example: f / 1.4, f / 2.8, f / 8, and so on. In this case, the plates of the device form a small hole between the photo lenses, comparable to a point. The second function of the aperture is to change the depth of field (DOF).
With a strong aperture, all objects that are within the values marked on the adjusting ring will be sharply displayed. In TTL SLR cameras, where the subject is viewed through optics coupled to the viewfinder through a prism and a system of mirrors, a “jumping” aperture is used. Focusing is carried out when the lens is fully open and only now of shooting the device instantly sets the preselected aperture value.
To optimize the shooting process, when it is not possible to use a tripod at long exposures, an optical image stabilization device is used. The device is based on gyroscopic sensors and a lens that can move freely in all planes. The data from the gyroscopic sensors are sent to the microprocessor, and by sending impulses to the electromagnets, it compensates for the movement of the camera by shifting the lens in the opposite direction.
Interchangeable lenses can be attached to the camera body in two ways:
Threaded Mount. Threaded lenses were used on older film cameras and are almost never used today.
Bayonet Device. The mount “bayonet” quickly and reliably fixes the optics on the camera with a special latch. Such a device allows the use of lenses with electronic control systems. For this, electrical contacts are provided on the body of the optics and the body of the camera, which are reliably closed after the installation and fixation of the optics.
According to experienced photographers, it is a good lens, not a camera, that is the key to quality photographs. Using high-end optics and a mediocre camera, you can get great pictures, but a poor-quality lens, even on a professional camera, can ruin the most winning scene. Often optics, in terms of cost, can be several times more expensive than a good camera. This is mainly determined by the materials of construction.
The highest quality and most expensive representatives of the class contain fluorite lenses in their device. The optics body is made of ultra-light alloys that are used in space technology. These lenses are highly reliable and long-lasting.
Next are the lenses with quartz glass lenses. They provide good photo quality and are quite reliable.
In last place in terms of quality are lenses with acrylic lenses and a plastic housing. It is especially bad if the bayonet mount is made of plastic. Backlash will be ensured with frequent replacement of optics even after a short time, and plastic lenses will quickly become cloudy from traces of dust and sand.
The lens is an integral part of the camera. It can be made as a simple aplanatic system and without various additional improving mechanisms. And in the form of a complex bulky optical system, which includes about 20 lenses divided into blocks, automatic focusing systems, focal length changes, image stabilization and various technological tricks that improve the quality of the captured image. The cost of a lens can vary from easily lifted to almost any amateur photographer, to prohibitively expensive – more expensive than a professional camera.
Types of Lenses
There are several types of lenses in market, here we will see the main type of lenses.
A standard or conventional lens is one that has the same angle of view as the human eye without side vision. The focal length of such a lens is approximately equal to the frame diagonal. Almost always, such lenses have a high aperture (this is characterized by the aperture value), which allows you to photograph at relatively short shutter speeds in low light.
Wide-angle lenses cover more angles than standard lenses. The shorter the focal length of the lens, the wider its angle of view. A lens with a focal length of 20 millimeters (for a 35mm camera) sees about 90 degrees of space along the frame diagonal. All lenses with a focal length of 20 to 50 mm can be called wide-angle.
Ultra-wide-angle lenses are lenses with a focal length of 14 to 20 millimeters. They can be divided into two groups. These are straight lenses that produce images with either no distortion or an acceptable level of perspective distortion, and distortion, resulting in barrel distortion. Distributing lenses are called fisheye (the name originated from the visual similarity between the front lens of the objective and the fisheye).
There are two types of fisheye lenses: 180 degrees diagonal of the frame (16mm) and 180 degrees vertical of the frame (8mm). With the help of the “fisheye”, you can get an original effect and a kind of expressiveness. Ultra-wide-angle lenses are used in reportage, architectural, interior and landscape photography.
Telephoto (Long Focal) Lens
Long focal lenses bring the subject closer to the photographer. They can also be divided into two types: telephoto and ultra-telephoto lenses. They differ structurally. In telephoto lenses, a negative lens has been added to the scheme, thanks to which manufacturers have achieved a significant reduction in overall dimensions. If you compare two lenses with the same focal length, then a telephoto lens will be significantly smaller in size and weight. But it so happened that all telephoto lenses are also called zoom lenses.
Telescopic (Super Long Throw) Lens
These are lenses with a focal length of 500mm or more. There are lenses with a focal length of 2000mm, but this is already a rarity. The weight of such lenses is more than 6 kilograms and shooting with them without a tripod is almost impossible. Almost all of them are equipped with a special tripod mount. A constructive type of ultra-long-focus lenses is a mirror lens. In such a design, spherical mirrors are part of the optical design. This design significantly reduces the weight and size of the lens, but it has some drawbacks. Unfortunately, it is impossible to install a variable aperture in such lenses, which means that the exposure will have to be adjusted only with shutter speed and sensitivity. The light-tone pattern of such lenses is extraordinarily beautiful, it is almost impossible to repeat it with any other lens.
This is the name for variable focal length lenses. Modern manufacturers can please you with a huge range of lenses of this type. These lenses are convenient: one such lens can replace several. You can more accurately build a composition, significantly increase the efficiency of work, for example, in reportage, wedding or sports photography. But not everything is as good as it seems at first glance.
Zoom lenses have drawbacks. Short throw zoom lenses suffer from distortion, and the shorter the focal length (larger field of view), the higher the distortion. In terms of aperture ratio, such lenses are divided into two categories: fixed and variable aperture. In the case of a variable aperture, the aperture changes depending on the change in focal length. For example, a 28-70 lens at a focal length of 28 mm has an aperture (aperture) of 2.8, and at 70 mm – 4. This impairs usability. The larger the focal length, the less aperture of such lenses. Constant aperture lenses have no such disadvantages. As the saying goes, you must pay for everything in the world, and for the constant aperture of zoom lenses. They usually cost 1.5 to 2 times more than variable aperture.
A soft-focus lens or soft lens is usually produced with a set of removable apertures. In such a diaphragm, the central opening (not equal to a specific working diaphragm) is surrounded by many smaller openings. The center hole creates a sharp image, while the outer smaller holes scatter it. The diffusion level can be adjusted by replacing the insert diaphragm. This makes it possible to significantly change the soft-focus effect and the degree of diffusion. In some models, spherical aberration is not fully corrected on purpose.
A lens that allows you to shoot without special equipment at a 1:1 scale. These lenses, unlike all the others, have aberrations corrected when shooting at a finite distance.
You may also like to read: Zeiss Milvus 2/100m Macro Lens: The Review
The name comes from the English word Shift, with the help of such a lens you can get rid of perspective distortions by shifting the lens block parallel to the plane of the film or matrix. It is the premier lens for those who want to capture architecture, cityscapes or still life’s without perspective distortion. When shooting, the camera is positioned so that the optical axis of the lens is parallel to the ground. When shooting from bottom to top, it is necessary to move the lens unit to ensure that the upper parts of the objects enter the frame. Accordingly, when shooting from top to bottom, the opposite is true.
There is certainly a constructive limit to this shift. And not always, for example, because of the height of buildings, it is possible to get rid of distortions. At the very least, perspective distortion will be minimal. The cost of shift lenses is higher than that of conventional wide-angle lenses of the same focal length. Image processing software such as Photoshop can simulate perspective distortion correction. Why imitation, because in real shooting a different perspective effect is created. Sometimes this fix is noticeable. It is important to remember that interpolation occurs during computer distortion correction, which means that if there are many small details in the frame, then the deterioration of quality will be inevitable. If the sky occupies most of the image, interpolation will not be noticeable.
Structurally, the teleconverter cannot be classified as a lens. But with its help, you can increase the focal length, which means it will get closer to the subject. Small size and light weight are the main advantages of the teleconverter. The advantages include a relatively low cost. Converters are produced with different magnification of the focal length. But the gain in focal length must be paid for by the loss of luminosity. If the converter has a magnification of 1.5, then the aperture ratio drops by one stop if the magnification is 2 by 2 stops. If you rarely use a long focal length, then it makes sense to purchase a teleconverter. But if you are shooting sports, concerts, or other subjects that require a lot of zoom, then it is worth getting a good telephoto lens.
Choosing A Lens for Your Camera
When choosing a lens, a beginner needs to focus first on the focal length. The tasks is to find which wide-angle, normal or zoom lenses can be used for photography, and are well known & reliable. Bellow table can help you to choose the lens type for your photographic requirements.
|Focal Length||Lens||Goals of Photography||Vision Angle|
|4 – 16 mm||Fish Eye||Landscape, Art, Specific Landscapes||180° and more|
|10 – 24 mm||Super Wide Angle||Interior, Landscape, Deliberate Distortion of Proportions||84 – 109°|
|24 – 35 mm||Wide Angle||Landscape, Architecture, Street Photography||62 – 84°|
|50 mm (35-65)||Standard||Landscape, Portrait, Close-Up and many more…||46° (32 – 62)|
|65 – 300 mm||Zoom||Portrait, Sport, Nature, Macro, etc..||8 – 32°|
|300 – 600mm + more||Ultra Zoom (Telephoto)||Wildlife and Sports from a Long Distance||4 – 8°|
We will now combine the lens, the subject of photography and the focal length into a simpler and more descriptive table. At the same time, one should understand the conventionality of any figure; it is impossible to argue that you cannot shoot people in full growth with a 300 mm lens, or, say, a 24 mm wide-angle lens. Yes, even a fisheye. But for classic portraits, it is still better to use the indicated focal lengths, because here the geometric distortions inherent in wide-angle lenses are unacceptable.
|Landscape & Interior||Wide Angle||Up to 35 mm|
|People (Full Size)||Wide Angle||35-50 mm|
|Classic Portrait||Standard + Zoom||50-135 mm|
|Shooting Distant Objects||Telephoto (Ultra Zoom)||from 135 mm|
In addition to the focal length, the lens aperture is also very important. What it is? Aperture is (very roughly) the ratio of the diameter of the aperture opening to the focal length of the lens. To put it even rougher, it’s just the size of the hole in the lens. 😊😊😊 And the larger it is, the more light comes in and it is better to shoot in low light. The aperture size can be adjusted with the aperture to control depth of field and eliminate possible distortion.
Typical values are:
1: 1.4, 1: 2, 1: 2.8, 1: 4, 1: 5.6 , etc.
On the lenses themselves, the aperture ratio is exactly what they denote: through the colon space. The smaller the fraction, the smaller the aperture opening and vice versa. On all sites and in the literature, the designations 1/1.4, 1/2.0, 1/2.8, 1/4, 1/5.6 … For brevity, the unit in front is often discarded, for example: 1.4, 2.0, 2.8… So often, instead of one, the letter “f” can be used: f/1.4, f/2.0, f/5.6, etc…
And also without a fraction: f1.4, f2.0, f5.6, etc…
Lens Aperture Ratio: Slow or Fast
Lenses are fast and also slow or not very fast. What does it depend on? The maximum amount of light that can pass through the optical system of a lens is limited by the diameter of the lens in its barrel. The larger this diameter, the more light will pass through, and the higher the aperture ratio. And the higher, of course, the dimensions, weight and price: generally the thicker the lens, the more expensive… 😉😉😉
Of course, I was joking. The price also depends on the quality of the lens manufacturing, their grinding, coating, lens assembly and the quality of all its components. But back to the aperture ratio.
Aperture above f/2.8 (for example – f/2, f/1.8, f/1.4, f/1.2) characterizes as fast lens, but f/3.5 and below is slow or dark.
Everything is simple here: the larger the hole, the more light comes in, the better. Some amateur photographers seek to purchase the highest aperture lens, believing that it is easier for them to shoot in low light conditions, and that such optics have wider possibilities for aperture control.
That’s right, but even if you don’t take into account the sobering blow to your wallet, you should always understand two things:
1. Even a very high aperture ratio of a lens is not an indicator of its quality, especially for inexpensive lenses from little-known companies. One of Zeiss Ikon specialists Wolf Veran once said: “It is not the absolute maximum aperture that is important, the maximum aperture at which the lens is able to create a high-quality image is important.”
Let me explain what has been said. Usually, to eliminate possible distortions and obtain sufficient sharpness, the photographer tightens the aperture: it is normal if by 1-2 stops, and great if it is not necessary to do this. If high-aperture optics have to cover the aperture up to f/5.6 in order to get an acceptable picture, then such a lens is not worth the price.
On the other hand,5.6-8.0. It is outside this range that optical distortions of all sorts begin, for example, drop in detail caused by open holes (and diffraction by closed ones). No need to look at hundreds of tests, we know from experience. But in high-quality optics, aberrations will not be critical for photography at an open aperture, and only then a high aperture ratio is a huge plus.
2. A high-aperture lens by itself does not give an interesting and creatively high-quality photograph.
Well, the advantages of such optics are well known. The fast lens is ideal for working in low light conditions, indispensable for photographing portraits and attracts with the ability to change the depth of field in a wider range.
When choosing a lens, in any case, I recommend starting with such concepts as focal length and aperture ratio: they are easily checked upon purchase, because all this is written on the lens itself.
For those who choose interchangeable optics, it is useful to know its designations. The table, which is available in a more detailed article, marking the lenses, I have given below and here it will come in handy.
|For full frame (FF)||EF||FX||FA||–||DG||–|
|For Crop Only (APS-C Matrix)||EF-S||DX||DA||DT||DC||DI II|
|Image Stabilizer||IS||VR||In the Cell||In the Cell||OS||VC|
|Low Dispersion Lenses||UD||ED||ED||–||–||LD/AD|
The hyphen “-” in the table means the absence of this characteristic (or the absence of the required information). Full frame lenses can generally be set to crop (APC-S sensor), but not vice versa.
1. How to find out the focal length and aperture of the lens?
They are indicated next to the frame. For example, consider the ancient Helios lens – we take it in our hands directly from the picture and just read it.
Let’s start with the camera lens named ‘MC Helios-44K-4’. This model has a multi-layer coating (letters “MC”) and a bayonet mount “K” (the letters are visible in the name). Coating is needed to reduce light reflection from the lens surface, and with the “K” mount, the optics can be installed on any camera with the same mount (and without any adapters), For example, on any Pentax SLR – even a digital one. The lens has a constant focal length of 58 mm (see on the left), the aperture is indicated next to it – f/2 (designated 1:2). There is also a mounting thread for light filters – M52x0.75, optics were produced for Zenit cameras with “K” mount.
2. What is lens mount and bayonet?
A lens mount or bayonet is an interface – mechanical and often also electrical – between a photographic camera body and a lens.
3. What is minimum focusing distance (MDF)?
MDF affects the zoom ability of the lens and one of the main characteristics of a macro lens is that the shorter the focusing distance, the better. allows you to focus on the subject from an extremely short distance (sometimes very close to the lens), i.e. capture “more object” into the frame. MDF begins its countdown from the plane of the matrix and with macro lenses this distance is always less than that of conventional optics with the same focal length.