How many kinds of camera lenses are there? Talk about the advantages of each type and the comparison of each type in detail.

With the rapid development of science and technology, the cameras produced are varied, varied, complicated in structure and precise in machinery, and new products emerge one after another.

No matter how various cameras change and how complicated the structure is, the basic structure is the same:

First, an imaging system, that is, a lens, is needed to form an optical image of a special object;

The second is to have an exposure channel from the lens to the film, that is, a black box;

Third, there must be a carrier, that is, the fuselage, which can hold all the components;

The fourth is to have a device that can hold photosensitive film, that is, the back. So the basic structure of all cameras is four parts-lens, camera box, body and back. The details of these four parts are as follows:

① lens part

The lens made of optical glass gathers the light entering the lens to form a clear image on the photosensitive film. More complex lenses are composed of two or more pieces of optical glass, which are called lens units. The transmission unit forms a whole, which is the photographic lens.

The lens of a camera includes a lens group, an aperture and a shutter.

The lens is composed of lenses, and the number and group of lenses determine the quality of the lens.

Aperture consists of many multigenus leaves. It controls the amount of light entering the film by controlling the size of the lens aperture. When controlling the expansion and contraction of the blade, the light entrance hole is made larger and smaller, thus controlling the size of the light beam projected onto the film through the lens. The numerical value of this aperture size is marked on the lens with the aperture number or F/ value.

Louvers are made of metal sheets or colloidal wires. It controls the exposure time, that is, the time when light enters the camera and reflects on the film. Correct exposure can make the subject get a clear image.

Lens type:

There are many kinds of lenses, and there is no "best" lens. Because all kinds of lenses have unique functions, scope of application and advantages, it is correct to choose lenses for shooting needs.

According to the different effects of shooting pictures and the length of camera lens focal length, the usual lens types are: standard lens, wide-angle lens, telephoto lens, fisheye lens, reflective lens, zoom lens and special lens.

● Standard lens

The standard lens is a well-calibrated positive lens, whose focal length is equal to or close to the diagonal of the negative image frame used, and the viewing angle is similar to that of the human eye. If the frame of 135 camera is 56×56 mm, then its standard lens focal length is 50 mm ... So the imaging effect of the standard lens, such as the range of the scene and the perspective brought by the size ratio of the front and rear scenes, is similar to that of the human eye. The picture image is more realistic and natural, and the imaging quality is relatively high, so it is widely used in various photography and has strong adaptability. Anyone who requires the subject to conform to the normal proportional relationship must rely on the standard lens to shoot. It is the most widely used lens.

● Wide-angle and ultra-wide-angle lenses

Wide-angle lenses are characterized by short focal length, wide viewing angle and long depth of field, all of which are larger than standard lenses. Its angle of view is beyond the normal range of human eyes.

A lens with a viewing angle of about 70 degrees to 90 degrees is a wide-angle lens; Its viewing angle is about 100 degrees, which is called super wide-angle lens. The biggest advantage of this lens is that it can shoot large scenes in a short distance.

Its specific characteristics and uses are as follows: the depth of field is large, which is beneficial to clearly show the subject with large vertical concentration on the screen; Wide viewing angle is conducive to shooting a wider scene in a narrow environment; The depth of field is long, which can make the proportion of near-large and far-small scenes strong in depth and make the picture have a strong sense of perspective. Its disadvantage is that the image distortion is quite different, especially at the edge of the picture, so we should pay attention to the distortion when shooting close-range.

● telephoto and ultra-telephoto lenses

This kind of lens, also called long focal length lens, has the function of a telescope.

This kind of lens has a longer focal length and a smaller viewing angle than the standard lens. For example, a 135 camera with a focal length of about 200mm and a viewing angle of about 12 degrees is called a telephoto lens, and a camera with a focal length of more than 300mm and a viewing angle of less than 8 degrees is called a super telephoto lens.

This kind of lens has the following characteristics: the depth of field is small, which is beneficial to capture the image of the combination of reality and reality; The viewing angle is small, so you can shoot larger scene images from a distance, and you can shoot inaccessible objects such as animals, scenery, human natural expressions, etc., without interference from a distance; The perspective relationship is greatly compressed, which reduces the proportion of near to large and far to small, makes the foreground and background of the picture very compact and shortens the depth of the picture; The difference of image distortion is small, which is especially good in portrait.

● Fisheye lens and reflector

Fisheye lens is an extreme ultra-wide-angle lens. For 135 camera, it means that the focal length is below 16mm and the viewing angle is about 180 degrees, so it is named because of its huge viewing angle such as fisheye. Its shooting range is very wide, which can greatly exaggerate the perspective effect of the scene. It makes the picture seriously barrel-shaped, so it has a special taste.

Reflective lens is a kind of super telephoto lens, which is short and fat in appearance, half shorter than telephoto lens with the same focal length, light in weight and flexible and convenient to use. Its disadvantage is that there is only one aperture, which is not conducive to depth of field control.

● Zoom lens

Zoom is a lens whose focal length can be changed. The focal length is the distance from the center of the lens to the clear image formed on the film. The focal length determines the size of the image formed by the subject on the film. The larger the focal length, the larger the image.

Zoom lens is a very attractive lens. Its lens focal length can be adjusted freely in a large range, which means that the photographer can adjust the imaging ratio of the negative film in a large range without changing the shooting distance, which means that a zoom lens actually plays the role of several fixed-focus lenses with different focal lengths. 1959 The world's first zoom lens for photography came out, and the focal length changed from 36 to 92 mm, which was used in 135 camera. There are more and more kinds of modern zoom lenses, and the imaging quality is getting higher and higher, which is more and more favored by photographers.

1. Type of zoom lens

There are many kinds of modern zoom lenses, generally speaking, there are two categories: automatic zoom and manual zoom. The former is used for autofocus cameras and the latter is used for manual focus cameras. Whether it is automatic zoom or manual zoom, from wide-angle zoom lens to telephoto zoom lens. Practical knowledge about zoom lens types includes the following aspects.

Zoom range-From the zoom range, the basic types are: wide-angle zoom lens of about 20-35mm, standard zoom lens of about 35-70mm, cosco zoom lens of about 70-2 10mm, telephoto zoom lens of about 200-400mm, etc.

Zoom ratio-From the zoom ratio, the basic types are 2 times, 3 times, 4 times, 5 times and 6 times. 20-35mm, 25-50mm, 28-55mm, 35-70mm, 75-150mm,100-200mm, 200-400mm and so on. The third time is mainly 28-85 mm, 35- 105 mm, 70-2 10 mm, 85-250 mm, 100-300 mm, etc. The fourth time is mainly 50-200 mm, 150-600 mm, etc. Five times, mainly 28- 135 mm, 50-250 mm, etc. Six times are mainly 35-210mm and 50-300mm.

Zoom mode-Manual zoom can be divided into "single-ring push-pull type" and "double-ring rotary type".

The "single-ring push-pull" zoom ring is also a focus ring. Push and pull back to zoom and rotate to focus. It has the advantages of convenient use and quick shooting, but it also has some disadvantages, such as simple sliding of the lens when shooting up and down; Focus first and then zoom, which is prone to focus shift and affects imaging clarity.

The "double-ring rotary" zoom ring and focus ring are independent of each other, and the rotation operation does not affect each other, so there is no disadvantage of single-ring push-pull type, but the operation is not as simple as single-ring push-pull type, especially when the stunt of "zoom shooting explosion effect" is used.

2. Advantages and disadvantages of zoom lens

The biggest advantage of zoom lens is that a variable lens can replace several fixed-focus lenses, so it is very convenient to carry and use. You don't have to constantly change lenses when shooting, and you don't have to run back and forth to take pictures of the same object in different scenes.

The main disadvantage of zoom lens is its small aperture, which will bring trouble to shooting, such as when you want to use high-speed shutter speed and large aperture. , often can't meet the needs. The viewfinder screen after using the zoom lens is not as bright as the fixed-focus lens, and it is often unable to indicate the focus of the segmented image. In addition, under the premise of the same production technology level, the imaging quality of zoom lens is always worse than that of fixed focus lens.

3. Selection of zoom lens

Equipped with zoom lens-unless telephoto is particularly needed, wide-angle, standard and medium-focus zoom lenses should be selected, such as 28-85 mm, 28- 135 mm, 35-70 mm, 35- 105 mm and 35-265438. Although the zoom magnification of "35-70 mm" is small, it is good at being thin and light, and the price is relatively low, which can also meet a large number of daily shooting needs. Some modern cameras have replaced the original 50 mm fixed-focus standard lens. The focal length range of "28- 135 mm" is ideal, but it is off-set and the price is relatively high. "28-85 mm" is very suitable for photographers who often shoot indoors; "35-2 10 mm" has a large zoom range and great applicability, but it is too big and heavy, which brings inconvenience to shooting. It is not wise to consider only the zoom ratio.

Equipped with two zoom lenses-two zoom lenses in hand, which can meet almost all kinds of shooting needs. The basic consideration in choosing two zoom lenses is to include all the commonly used focal lengths, and not to let the zoom ranges of the two zoom lenses overlap too much. Based on this guiding ideology, the basic choices are "35-70mm" plus "70-210mm", "28-85mm" plus "85-250mm", "24-50mm" plus "50-250mm" and so on. If your lens is mainly used for telephoto, then "150-600 mm" is ideal, and you can add "28- 135 mm" or "35- 105 mm".

It is also important to make the zoom operations of the two zoom lenses as consistent as possible. "Push-pull" and "rotation" have their own advantages and disadvantages. As long as they are consistent and practice makes perfect, they are easy to use.

● Special lens

The special lenses used by the parties are "colossus lens", "angle adjustment lens", "soft focus lens" and "zoom lens".

1. colossus lens

"Colossus lens", also known as "macro lens", is a kind of lens that can produce colossus effect. Can be divided into "special type" and "general type".

The special giant lens can only be used for close-up, and it can be used with close-up leather cavity or close-up tube to obtain high-magnification images. The focal length is 20, 38, 50, 80, 135mm, etc. The shorter the focal length, the greater the magnification. For example, the "Zuiko 20mm" colossus lens, combined with a close-up skin cavity, can capture an image 4- 12 times the original size. 12 times means that the body of "2×3mm" can be filled with 135 frames of "24×36mm". Universal Ponzi lens can be used as both a short-distance Ponzi lens and a long-distance ordinary lens. Its close-up magnification is small, which is not as good as a special colossus lens. For example, the maximum close-up effect of "Zuiko 135mm" combined with "automatic close-up tube 65- 1 16" is 0.5 times of the original size; It can focus in the range of 37 cm-∞ and can be used as a 135mm lens. Although the ordinary fixed-focus lens has a huge image effect after using the close-up lens, it can't focus at a long distance.

Some zoom lenses also have the giant image function (the lens is marked with "macro"), but their giant image magnification and imaging quality are not as good as those of fixed-focus giant image lenses. There are three ways to adjust the macro image file of zoom lens: some zoom to telephoto, some zoom to short focus, and some adjust the macro image file at zoom.

2. Angle adjusting lens

Refers to the lens with the function of correcting the upward contraction of the vertical line of high-rise buildings. The main optical axis of the lens optical system can be adjusted horizontally or vertically, and the positions of the body and the film plane do not move during adjustment. The angle adjusting lens is mainly used for architectural photography.

3. Soft focal length lens

"Soft-focus lens", also known as "soft-focus lens" and "soft-light lens", is a kind of lens that can slightly blur the image and is mainly used for portrait and landscape photography.

The soft-focus effect of soft-focus lens is different from the usual lens focusing. In essence, soft-focus lens produces ghost, clear real image and out-of-focus virtual image, which overlap.

4. Zoom additional mirror

"zoom lens" is the abbreviation of "zoom lens", commonly known as "extended range lens" In fact, the extended-range lens is just one of them. Additional zoom lenses are mainly divided into telephoto zoom lenses, wide-angle zoom lenses and super-large zoom lenses according to their functions. When you have a single-lens reflex camera with standard lens, adding this zoom additional lens can not only achieve the effect of telephoto wide-angle and giant lens, but also reduce the cost.

In order to use the lens better, it is necessary to emphasize the focal length and imaging effect here.

The meaning of lens focal length can be understood as "the distance from the lens center to the film plane" from a practical point of view. Theoretically, the calculation of focal length refers to the vertical distance from the second node of the lens (or lens group) to the focal plane when the scene at infinity forms a clear image on the focal plane. The second node is located very close to the center of the lens, usually a little behind the center of the lens.

The second node is also the optical center. The optical center of the lens can also be located outside the lens. The lens designed according to this principle is also called "back focus lens". "Back-focus lens" is a key to the development of modern lens. This is why lenses with the same focal length can have different lengths.

The range of the focal length of modern camera lens has been as short as 6mm and as long as 2000 mm Facing the same shooting object and the camera with the same frame, the change of imaging effect caused by focal length change can be summarized as the following two laws.

1. The focal length is inversely proportional to the viewing angle.

Long focal length and small viewing angle; Short focal length and large viewing angle. Small viewing angle means that you can shoot a large image ratio from a long distance; Large viewing angle can capture a wide range of scenery at close range.

2. The focal length is inversely proportional to the depth of field

Long focal length and small depth of field; Short focal length and large depth of field. Depth of field is related to the image clarity of deep scenes, which is an important practical and theoretical problem in photography.

Aperture on the lens:

● The function of aperture-both aperture and shutter are used to control luminous flux. Only by mutual restriction and cooperation can the photographic film be exposed correctly.

In the structure of photographic lens, aperture is one of the important devices.

The function of aperture is to adjust the luminous flux of lenses with different apertures. The aperture of the early simple crescent Dan Toujing camera is to drill some circular holes with different specifications on the metal plate and install them in front or behind the lens. Move the metal plate to make the circular holes aim at the center of the lens, so as to adjust the luminous flux. The aperture of modern compound lens is composed of many arc-shaped metal blades with variable aperture, which are installed between lens groups of the lens, and the aperture of the aperture can be adjusted at will as needed.

The function of the aperture is to accurately adjust and control the luminous flux of the lens and correctly expose the photosensitive materials; Under the condition of reducing the aperture, some residual aberrations of the lens can be reduced; The depth of field can be controlled by the contraction or enlargement of the aperture, with small aperture and long depth of field, and large aperture and short depth of field.

● Marking of holes

The marks of holes are arranged in a series of √2. So we choose √2 as the common ratio because √ 22 = 2, that is, every step of aperture difference, the aperture area is twice as bad, and the light transmission is twice as bad, so every two adjacent readings become a multiple relationship.

According to the time series of √2, the step-by-step data are as follows:

√2……………………………… 1.4

√22………………………………2

√23………………………………2.8

√24………………………………4

√25………………………………5.6

√26………………………………8

√27……………………………… 1 1

√28……………………………… 16

√29………………………………22

√2 10………………………………32

The engraving coefficient of lens is to arrange this series of numbers into geometric series. The luminous flux of each level coefficient is calculated by the aperture area, regardless of the light transmittance of the lens. For example, on the standard scale, if the aperture increases by one level, the lens transmittance will increase by two times; When the aperture is reduced by one level, the lens transmission power is reduced to 1/2. Every difference in aperture doubles the exposure. This is easy to master and use in photography practice.

The aperture coefficient of each aperture is the ratio of the diameter of the incident beam to the focal length, which is called the focal length number. The aperture coefficient of modern lens is divided into two systems: English system and European system:

British system 2.845.6811162232

Continental system 2.23.24.56.3912.518 25

There is no difference in the usage of the coefficients of the above two systems in photography practice. In addition, the aperture coefficient is also calibrated by the level coefficient, which is called the proportional system. In the early days, simple and fast straight lens was used, and the aperture coefficient was determined by grade coefficient. Now compare the focal length coefficient and grade coefficient of the aperture:

The distance from the focus is 45.6811.31622.632.

Grade coefficient (equal ratio system) 1 2 4 8 16 32 64

From the above comparison, it can be seen that the sizes of grade coefficient light holes are arranged in the order of equal ratio system. The larger the aperture, the smaller the reading and the less exposure time required. This scale represents the relative exposure time, not the relative aperture. It is very convenient to calculate when using. Some photographic lenses specially used for shooting documents and materials use this grade coefficient to mark the aperture coefficient.