Why not just use the relative aperture to represent the aperture factor and its reciprocal to it

Because the aperture size is not the physical size (although it is proportional), but the amount per unit time, for example, if the lens uses more glass than the B lens, the light transmittance will be caused.

low, then in order to achieve the same amount of time per unit of time.

The relative aperture is a ratio. The size of the relative aperture indicates how much light the lens absorbs. The reciprocal of the relative aperture is called the aperture number or aperture coefficient. The largest relative aperture is engraved on the lens. 1: Better than 1:4.

Usually except for wide-angle lenses.

In addition, the diameter of the front lens is approximately equal to the diameter of the beam, so the effective aperture of the lens is the maximum aperture of the lens, that is, the maximum aperture of the lens.

Because the aperture size is not the physical size (although it is proportional), but the amount per unit time, if the A lens uses more glass than the B lens and the light transmittance is low, then in order to achieve the same amount of time per unit time.

The relative aperture is a ratio. The size of the relative aperture indicates how much light the lens absorbs. The reciprocal of the relative aperture is called the aperture number or aperture coefficient. The largest relative aperture is engraved on the lens. 1: Better than 1:4.

The effective aperture of a lens refers to the diameter of the beam that passes through the lens in front of the lens. Usually except for wide-angle lenses, the diameter of the front lens is about equal to the diameter of the beam, so the effective aperture of the lens is the maximum first-order aperture of the lens, that is, the maximum aperture of the lens.

No one wants to count after the decimal point.

There is no difference between the aperture value and the aperture factor.

The aperture value is the relative value (the reciprocal of the relative aperture) derived from the focal length of the lens and the lens clear diameter. For example, for a standard 50mm lens, the maximum clear diameter is calculated to be 50mm, so that it can be understood that the maximum clear diameter of the same zoom lens is the same at different focal lengths, but the maximum aperture is different after conversion.

The aperture coefficient is the reciprocal of the "relative aperture". To control the amount of light entering the lens, it is necessary to control the so-called "aperture diaphragm" of the lens. In order to facilitate the calculation of the amount of ** in actual photography and to measure the actual effect of the aperture diaphragm of different lenses with a unified standard, the concept of "relative aperture" is adopted.

So the two are the same thing.

The aperture coefficient is the reciprocal of the "relative aperture".

To control the amount of light entering the lens, it is controlled by the so-called "diaphragm" of the lens.

Aperture diaphragms are located inside the lens and are usually composed of multiple movable metal blades (called diaphragm blades), which can make the (approximate) circular hole formed in the middle larger or smaller to achieve the purpose of controlling the amount of light passing through.

We use the term "aperture" to describe the light transmission capacity of a lens, and the aperture is controlled by the diaphragm.

For different lenses, the position of the diaphragm is different, the focal length is different, and the entrance pupil diameter is also different, and the aperture is used to describe the light transmission ability of the lens, and the comparison of different lenses cannot be realized.

In order to facilitate the calculation of the amount of ** in actual photography and to measure the actual effect of the aperture diaphragm of different lenses with a unified standard, the concept of "relative aperture" is adopted.

Relative aperture = [entrance pupil diameter] [lens focal length] = d f

A lot of information on the Internet has been written backwards, please note that the relative aperture and aperture coefficient (also known as the f-number) are reciprocal to each other.

Aperture factor = [lens focal length] [incident pupil diameter] = f d

For example, if the focal length of a lens is 50mm and the diameter of the entrance pupil is 25mm, then the relative aperture of the lens is 25 50 = 1 2. In actual use, the aperture coefficient is usually used to indirectly express the size of the relative aperture, such as etc., and there are also directly expressed by the relative aperture, such as 1:2,.

The full aperture factor values are, f1, f2, f4, f8, f11, f16, f22, f32, f44, f64

It is worth mentioning here that the smaller the aperture f-value, the more light will enter in the same unit time, and the amount of light entering the upper stage is just twice that of the next level, for example, the aperture is adjusted from f8 to, the amount of light entering is doubled, and we also say that the aperture is opened one step wider. For consumer digital cameras, the f-number of the aperture is often between -f16. In addition, many digital cameras can make 1-3 levels of adjustment when adjusting the aperture.

The multiple of the aperture value is called a stop, and if it is closed by a stop, the amount of light entering is twice as small.

Aperture factor = [lens focal length] [incident pupil diameter].

The complete sequence of aperture coefficient values is: f1, f2, f4, f8, f11, f16, f22, f32, f44, f64

If the aperture value sequence is set according to this standard, the luminous flux of the adjacent two levels of aperture coefficient is doubled (not doubled), such as f8 and f4, and ,...... f4

As can be seen from the above formula, the aperture coefficient is the reciprocal of the relative aperture (the diameter of the entrance pupil and the focal length of the lens), that is, the larger the aperture value, the smaller the relative aperture.

The diameter of the entrance pupil is proportional to the square of the area, and the transmission is proportional to the area of the incident pupil, so the diameter is squared to the transmission. Specific calculation: For example, the aperture of f8 has a relative aperture of 1 8 (in layman's terms, the diameter of the aperture is 1 8 of the focal length of the lens), and the aperture of the aperture is 1 (the diameter of the aperture is 1 of the focal length of the lens, and the clear area of the two is doubled, so the light transmission is naturally doubled.

The aperture value is the relative aperture "coefficient", which is the relative aperture, not the physical aperture of the aperture, and the aperture value is the relative value of the focal length of the lens divided by the clear diameter of the lens (the reciprocal of the relative aperture). So it can be said that these two words are the same thing.

(1) Actual caliber.

It refers to the ratio of the diameter of the front lens (within the lens pressure ring) to the focal length of the lens. However, this calculation is only rough and does not necessarily correspond to the actual amount of light entering the lens. The reason is that the optical structure of each type of lens is different, and the refraction angle formed by the light passing through each lens of the lens barrel is different, so it does not necessarily match the diameter of the front lens.

In addition, in order to avoid insufficient illumination at the four corners of the negative, some lenses will deliberately make the front lens larger. Therefore, expressing the luminous flux of the lens with the actual aperture does not necessarily conform to the above relationship.

2) Effective caliber.

In fact, the most accurate calculation of the lens aperture is determined by the ratio of the diameter of the beam actually passing through the front lens to the focal length of the lens. Therefore, what we usually call the lens caliber actually refers to the effective caliber of the lens. The caliber of the lens calibrated on the camera lens is, of course, the effective aperture determined in this way.

c) Relative caliber.

The effective aperture of the lens is determined by the maximum luminous flux of the lens, of course, in practical applications, we cannot shoot with the maximum aperture. The aperture (diaphragm) in the middle of the lens is a device that changes the luminous flux in a certain proportion. By changing the aperture, different luminous fluxes form different aperture grades.

Therefore, the aperture of the lens, which is controlled by the aperture, we call it the relative aperture.

From the above situation, we can see that most of the lens aperture we talk about refers to the effective aperture. The diameter of the mouth of the filter mounted on the front of the lens should not be confused with the lens aperture.

So what is the main role of large-aperture lenses for photography? The only purpose of a large-aperture lens is to increase the luminous flux, making it easy to shoot in situations where illuminance is insufficient, and there is no superiority when illumination allows. The reason for this is that increasing the aperture of the lens requires a breakthrough in more difficult optical corrections, which often requires the addition of lenses or special lenses.

This not only increases the weight of the lens, but also increases the production cost, which is why large aperture lenses with the same focal length tend to be much more expensive. In addition, although modern optical technology is very advanced and can produce large-aperture lenses with high optical quality, this does not mean that large-aperture lenses perform well in all situations. In general, any large-aperture lens doesn't perform best at full aperture, and manufacturers tend to recommend the best aperture.

Aperture affects aperture, but it is not absolute, the aperture is related to the focal length and the "equivalent clear aperture", which is the equivalent aperture, not the physical aperture; Because in the optical system of multiple lenses, the physical caliber is meaningless.

You said that 55, 52 is not strict, that is the filter caliber, which includes the shell of the lens itself, and it cannot be considered that 55 is necessarily larger than 52.

The larger the aperture, the larger the diffuse circle, resulting in a shallower depth of field, which is why it is easy to get a shallow depth of field with a DSLR lens and a shallow depth of field with a small DC lens.

The filter aperture of 50 and 50 is 52 mm, but you have to look at the lens, look at the structure of the two lenses, and you can see that the first lens is almost in the middle of the lens, and the size ratio is much smaller, and the larger aperture is not necessarily a good head, but the good head must be a larger aperture in the same focal length.

If the aperture is large and the aperture is small, the light is the same when the aperture is hit. The following is the relationship between aperture and aperture values.

The relative aperture is the focal length of the lens aperture, which is the ratio of the focal length to the lens aperture.

The reciprocal of the relative aperture aperture coefficient (aperture value).

For example, if the focal length of a lens is 50mm, the aperture is 4, and the effective aperture is 50 4

Aperture factor: The aperture factor is the value obtained by dividing the focal length of the lens by the diameter of the aperture and is denoted by f. For example, there are two lenses: A and B

A lens has a focal length of 50mm and a maximum aperture diameter of 25mm, so the aperture factor is 50 25 2, we say it is a lens of f2;

The focal length of the B lens is 35mm, the maximum aperture diameter is 17 5mm, and the aperture factor is 35 17 5 2, we also say that it is a lens of f2;

The aperture is large and can be shot in a darker environment.

The size of the lens aperture of the camera affects the amount of light transmitted.

The larger the aperture, the better, the imaging of the large-aperture lens is better than the small-aperture, your 55mm and 52mm are the filter aperture, and the lens aperture has no necessarily relationship, the lens aperture is expressed in the maximum aperture. That is, the lens with a larger aperture than the lens.

If the aperture is large and the aperture is small, hit the same aperture, then: the same luminous flux of the large aperture and the small aperture, but the luminous flux of a lens cannot be reached, and the same is half a stop at the maximum aperture. When shooting at aperture, the lens is shot with a wide open aperture, and the imaging is of course inferior to the quality of the lens that is smaller than the time.

The aperture is a device used to control the amount of light that passes through the lens and enters the photosensitive surface of the body, which is usually inside the lens. To express the aperture size, we use the f-number. For the already manufactured lens, we can't change the diameter of the lens at will, but we can control the amount of light transmitted through the lens by adding a polygon or a circular hole grating with a variable area inside the lens, which is called the aperture.

Aperture, which is equivalent to the pupil of our human eye, controls the amount of light entering the lens. And the greater the light, the more light it enters, and vice versa.

The aperture of the camera consists of a series of blades that form a circular hole in the **. Adjust the blades to adjust the size of the round hole. The larger the hole, the more light enters the camera and reaches the film.

From now on, we use the term aperture to represent a round hole formed by an aperture. "Aperture"It's just that"Round holes"Another way of saying it. Therefore, if you change the size of the aperture hole, you also change the aperture.

Adjusting the aperture can produce different sizes of apertures. In photographic techniques, the f-number is used to represent different sizes of apertures.

Now let's take a quick look at the different f-value meanings. We already know that the key is that the f-number, expressed by the maximum aperture of the lens, can describe a particular lens"Speed"For example, if the maximum aperture of a lens is marked as f 2, then the lens is called"The maximum aperture of f is marked as f 2, so the lens is called"f 2 lens"；If the maximum diameter of a lens is f, then it is called"f Lens".According to this strange logic, the smaller the f-number, the larger the aperture, and the more light the lens transmits.

One lens can take in more light than the other, so to speak"Comparatively fast"。So, the F lens is faster than the F 2 lens, the F 2 lens is faster than the F lens, and so on.

Aperture coefficient (relative aperture) = lens focal length] incident pupil diameter] = f d

For example, if the focal length of a lens is 50mm and the diameter of the entrance pupil is 25mm, then the relative aperture of the lens is 50 25=2.

Usually the way to express the relative aperture is to add [f] in front of the relative aperture, such as f and so on, and 1:2 is also used to represent f 2. Usually there are more 1:2 points on the lens markers.

In practice, the term "relative aperture" is rarely used, and it is usually called "f-stops", referred to as "aperture" or "f-factor".

Aperture range. The smaller the value after f, the smaller the camera's aperture can be reduced. The first sedan car.

The higher the value after f, the larger the camera's aperture can be. Wanton.

Generally, the minimum aperture of non-professional digital cameras is between f8 and f11, while professional digital cameras have a large area of sensors, and the lens is far away from the sensors, and the aperture value can be very small. For consumer digital cameras, the f-number of the aperture is often between -f16.