What are the front focus points of the camera?

Focus, in physics, refers to the convergence point of parallel light after refraction by lens or reflection by curved mirror.

In photography, in fact, the use of focus in the shooting process is the same as the focusing principle in physics, which reflects the difference of subject and focus, as well as the different shooting themes of scenes, people and things.

There are two ways to determine the position of two focal points. One is the front focal length and the back focal length relative to the first and last surfaces of the system. The front focal length is the distance from the object focus to the first surface of the system, and the back focal length is the distance from the image focus to the last surface of the system.

Another method is relative to the main plane of the system, that is, the so-called main focal length, object main focal length or first main focal length, which is the distance of object focal length relative to the first main plane of the system, and image main focal length or second main focal length is the distance of image focal length relative to the second main plane of the system.

The focal length value of a system often refers to the main focal length value. The plane perpendicular to the common axis of the optical system and passing through the focal point is the focal plane. Because there are two focal points, there are also two focal planes: the first focal plane (object focal plane) and the second focal plane (image focal plane).

Extended data

1. Plant shooting: focusing on flowers.

Flowers are undoubtedly the most attractive and beautiful part of growing pearls. So it is not difficult to understand that flowers are the most common focus choice in plant photography.

But when facing a bunch of flowers, we should first consider the most distinctive ones, such as the most beautiful ones, or the colors are different from other flowers; Then you can choose a flower that is slightly higher or closer to the camera than other flowers by observation. Through these methods, we can highlight this flower and make it an interesting center of the picture.

2. Take flowers at close range: Focus on stamens.

Close-up shot of flowers, the focus should clearly fall on the flower core. At this time, the close-up of the flower is enlarged, and the original colorful petals in the photo are mostly used as foil, while the delicate stamens in the flower core are arranged in an extremely regular way, which becomes a fascinating place.

3. When shooting close-ups, eyes are the key point.

Close-up photos of people are generally half-length photos focusing on people's faces. This kind of photos need to depict the character and even the heart through expressions.

When shooting close-ups of people, eyes are the first choice of focus. When a person's face is facing the camera, both eyes are on the same plane at this time, and either eye can focus; But this kind of framing will be peaceful, and then it will appear ordinary, so most photographers will take a half-side view of people and shoot it.

At this time, people's eyes will be in tandem. At this time, you need to focus on the eyes close to the camera for focusing shooting. Because its position is obviously more important than the eyes at the back.

4. When taking a full-length portrait of a person, the head is an important focus.

When shooting portraits including the whole body and the environment, the human eye can't focus clearly, so the key to choosing the focus quickly and conveniently is to focus on the head of the person.

Whether it is to show the movements or postures of the characters, the five senses of the characters are the key in the picture. Every move of people is controlled by the brain, so the head will become the center that affects the whole body. When shooting, you can focus on the face or head of the person in advance, and then quickly re-compose the picture when the whole body posture of the person reaches the ideal state.

5. Take photos of people and the environment: it is best to focus on people.

Such photos include simple souvenir photos, documentary photos and commercial photos. The photos of the combination of man and environment are the most vivid and the most difficult to take. However, whether people are the main body or the foil, most of these photos are taken with people as the focus, because people are the most active and emotional compared with those landscapes that are not moving or moving slowly.

Of course, when shooting with people as the focus, we should also pay attention to the depth of field to control the change of the actual environment. If people and scenery are simply needed to be clear, we can use a small aperture to obtain a large depth of field.

Baidu encyclopedia-focus

Baidu encyclopedia-photography

What does camera focusing mean?

Question 1: What is the camera focus? The focus is the place where the object is refracted by the convex mirror of the lens and converges into a similar point opposite to the direction of the lens, which is called the focus. In fact, it is not the focus, but the refracted image of the object is relatively small, and the vertical plane of this point can be called the focal plane. Refracted rays are clearest only when they converge on the plane where the focus is located.

Generally, the position of CCD or film is the position of focal plane. In order to shoot clearly, it is necessary to make the focal plane of CCD or film coincide with the refracted object, and the process of making the focal plane coincide is the process of adjusting the focal length.

Generally, only the lens of a SLR camera has an independent focus ring. It can be divided into auto focus and manual focus modes:

1. If any one of the digital camera and lens has a driving motor, then the automatic focusing can be realized through the electronic focusing system of the camera. Set the lens of the camera to autofocus, usually "A", aim the focusing instruction of the lens at the subject, and then press the shutter button halfway to autofocus.

2. If there is something wrong with the lens or motor of the camera, or if it can't focus automatically, you need to focus manually. Set the lens of the camera to "M" manual mode, and then focus by rotating the focus ring on the lens.

Question 2: What does focusing mean in a camera? Focus is focus.

Question 3: Focus in camera photography is a popular explanation of focus, that is, choosing the point with the clearest imaging.

For example, in a scene, some objects are far away from the lens and some objects are close to the lens. Choosing the focus is to choose which object to shoot clearly.

For example, people see things. When you look at the computer screen, the focus of your eyes is on the computer screen. What is behind the computer is seen by Yu Guang, so it is not clear. This is the so-called Jiao Wai. When you look out of the window, the focus is on the object you are looking at outside the window, and the computer that Yu Guang looks at is blurred.

The focal point in photography refers to the focal point, and the optical focal point refers to the convergence point of parallel rays refracted by a lens or reflected by a curved mirror. These two meanings are different.

Question 4: What is a fixed-focus camera? It is a camera that is clear from 1 m (possibly other values) to infinity.

No focusing mechanism, saving cost. This is the lowest camera.

Question 5: How does the camera set multi-focus? 1, you can select "autofocus selection mode", and the camera will automatically select the focus.

2. You can also select "Manual Focus Selection Mode" to control the focus yourself. At this time, it depends on whether the two subjects you shot are not in a focal plane. If it is (such as two people standing side by side), you can ensure that both themes are clear as long as you focus on a certain theme casually; If not (such as two people standing in tandem), you can only choose one subject that you think needs to be clear to focus on, and the other is not so clear.

Question 6: What is the key point in photography? Concentrate on one point, this part is the clearest part.

Question 7: What does the focal length of 35mm in the camera mean? If you say 35mm focal length, you mean 35mm focal length.

The focal length is the distance from the main point on the back of the lens to the CCD plane when the camera focuses at infinity. The CCD of a general digital camera is obviously much smaller than the standard 35mm film, so the actual focal length of a digital camera is usually very small. For example, the actual focal length of KodakDC5000 is only 6.5- 13mm. However, in order to facilitate buyers to have a unified concept of the focal length of digital cameras, most camera factories will do parallel calculation of the focal length of digital cameras according to the specifications of 35mm cameras, which is the so-called' 35mm equivalent'. When you see this data and compare it with the traditional lens focal length table in the appendix, you can have a general understanding of the lens performance of this digital camera. Reference example KodakDC5000 digital camera lens marking: 30-60mm (equivalent. )

1. Less than 20mm= super wide angle.

2.24 mm -35 mm = wide angle

3.50mm= normal viewing angle (approximately equal to the viewing angle of your eyes).

4.80mm-300mm= telescopic.

Above 5.300mm = super-telescopic.

So your 35mm focal length belongs to wide angle.

Question 8: What does focusing mean in photography? What's the use? Thank you. Focusing means adjusting the focal length. First of all, we must understand what is the point. For the human eye, the focus is the point you stare at, and the images before and after this point are the clearest. The lens of the camera is the same as this. Secondly, the focal length refers to the distance from the focal point to the lens. So the meaning of focus is clear, and its purpose is to make the object you want to express as clear as possible.

When you press the shutter halfway, the camera will automatically focus on a preset point (such as the middle of the picture), which is called autofocus.

Generally speaking, holding down the shutter for half a time is autofocus locking.

The function of autofocus lock is to lock the focus of autofocus and facilitate composition.

For example, the autofocus preset point of my camera is in the middle of the picture, and I want to shoot a flower, and this flower needs to be placed on the left side of the picture to achieve my shooting purpose. At this time, I can first put the flower in the middle of the picture and press the shutter for autofocus. After focusing, I can hold down the shutter for half a minute to lock the focus. Then I turn the camera slightly, put the flowers on the left side of the picture and press the shutter, and the work is finished.

If the camera has manual focusing function, just switch to manual focusing mode. Some cameras don't have this function.

The method of manual focusing to obtain clear focus can refer to the following steps: adjust the focal length in one direction (for example, from near to far), at this time, the subject will become clearer and clearer, and continue to adjust until the subject becomes blurred again after a certain point, and then slowly adjust it in the opposite direction, so that clear focus can be obtained by reciprocating several times.

Question 9: SLR camera focus 9 has 13. What does this mean? This is the number of focal points.

However, in fact, the most accurate and fastest focusing is cross focusing or double cross focusing.

So some cameras will mark 9 o'clock focus, center 1 cross focus, such as Canon 6D, and 19 cross focus, such as 7D.

There is a focus of 39 points and a cross focus of 9 points. Such as Nikon D7000.

Question 10: What does ALFOCUS on Canon cameras mean? Artificial intelligence autofocus (AIFOCUS).

This mode can judge the state of the subject and automatically switch between "single autofocus" and "artificial intelligence servo autofocus". After a single autofocus, if the subject moves, the camera will automatically switch to artificial intelligence servo autofocus to track the subject for focusing.

The focus of photography is the focus, and the popular explanation is to choose the clearest point of the image.

For example, in a scene, some objects are far away from the lens and some objects are close to the lens. Choosing the focus is to choose which object to shoot clearly.

For example, people see things. When you look at the computer screen, the focus of your eyes is on the computer screen. What is behind the computer is what Yu Guang saw, so you can't see it clearly. This is the so-called Jiao Wai. When you look out of the window, the focus is on the object you are looking at outside the window, and the computer that Yu Guang looks at is blurred.

The focal point in photography refers to the focal point, and the optical focal point refers to the convergence point of parallel rays refracted by a lens or reflected by a curved mirror. These two meanings are different.

What does the focus in photography mean?

Thank you for inviting me:

As for the word concentration, I saw it in junior high school physics textbooks. Its definition refers to the point where light parallel to the main optical axis will converge on the main optical axis after being refracted by a convex lens. We call it the focal point, and the distance from the focal point to the optical center of the convex lens is called the focal length, which is represented by the letter "F".

So how do we understand what is the focus in photography? Take our eyes for example, just like cameras, we can see objects clearly at ordinary times, but if we are nearsighted or farsighted, it means that the light can't converge on the retina (focus) well, and the objects we see become blurred.

Therefore, when we shoot with a SLR or a tool with photographic function, we must focus on it. Only when the focus is accurate can the theme be made clear.

For example, in the picture below, there is a flower in front and a flower in the back, but I focus on the front, so the flowers in the back will become blurred. With this concept,

Usually when we shoot flowers or portraits, we often use blurred background, which is how to achieve it.

Personal experience sharing, welcome your advice!

Photography Who can tell me what is focus, focal length and focus?

In a photo, the clearest part of the image is the focus.

The focal length is the distance from the lens center to the imaging plane (such as basement membrane or CCD).

Focusing, focusing includes manual focusing and automatic focusing. Focusing is a way of focusing by twisting the focusing ring and adjusting the camera lens to make the pictures clear. Simply put: it is to make the objects seen in the lens clear. The ultimate goal of "focus" is "focus".

Zooming in or out of the subject is called zooming.