What does the focal length of the camera mean?

Question 1: What do you mean by 3.6MM or 6MM written on the camera? focal distance

3.6mm surveillance lens is suitable for outdoor environments such as indoors and doorways, which need to expand the observation range.

6mm, 8mm and above surveillance lenses are suitable for high places.

Question 2: What does it mean to monitor the focal length in the camera? Many people who sell surveillance cameras don't understand the concept of focal length. They tell you how many millimeters the lens is. They don't understand whether this millimeter is the focal length or the lens aperture. They only know that they can see far or near.

Generally speaking, the larger the size of the fixed-focus surveillance camera, the larger the target you can see through the camera (that is, the farther you can see), but the narrower the viewing angle (the smaller the observation range) and the shorter the depth of field. The smaller the lens size, the smaller the target seen through the camera (that is, the closer it is), the wider the viewing angle (the larger the observation range) and the longer the depth of field.

Therefore, if you want to see a wider range, you should choose a small-caliber lens, but you should see a smaller target.

The width of the lens is the viewing angle, which is not provided by general camera manufacturers.

I hope I can help you. Don't be cheated.

Question 3: The focal length of the surveillance camera is 3.6 mm 4 mm 6 mm What do they mean? Mm is the aperture of the lens, and the greater the number of millimeters, the better. The smaller the lens, the wider the picture, and the narrower and clearer the picture. A lens with a number of millimeters is equivalent to enlarging the picture locally. According to the needs of the venue, the price of lenses with a few millimeters is the same. The following is a schematic diagram, which you will understand after reading. I hope it will be adopted.

Question 4: What does the focal length of the camera mean? The focal length refers to the distance from the center of the lens to the imaging sensor. The focal length represents the viewing angle. The shorter the focal length, the wider the visual range, and the longer the focal length, the smaller the visual range, but the larger the shooting ratio of distant objects.

Question 5: What does the camera's 16mm mean and how to adjust the focal length? 16mm means that the focal length of the lens is 16mm, and the lens with fixed focal length cannot be adjusted.

Commonly used specifications are 4mm, 6mm, 8mm, 16mm, and 25 mm. The field of view angles are about 80 degrees 65 degrees 50 degrees 30 degrees 15 degrees, and the effective distances are 10 meters 20 meters 30 meters 40 meters 50 meters respectively.

Question 6: What does it mean to monitor the focal length of the camera? Focal length is a measure of light convergence or divergence in an optical system, which refers to the distance from the optical center of the lens to the focal point of light convergence when parallel light is incident. It is also the distance from the center of the lens to the imaging plane such as the backplane or CCD in the camera. An optical system with a short focal length has a better ability to collect light than an optical system with a long focal length. Simply put, the focal length is the distance from the focal point to the center of the mirror.

Question 7: Is there a difference between the focal length of a lens and the focal length of a camera?

1. The focus is the point where the lens (or curved mirror) converges light, which can scorch the object.

2. Lens focal length: refers to the distance from the main point to the focus after lens optics, which is an important performance index of the lens. The focal length of the lens determines the imaging size, field of view compensation, depth of field and perspective of the picture. The focal length of a lens is a very important index of the lens. The focal length of the lens determines the imaging size of the object on the imaging medium (film or CCD, etc.). ), which is equivalent to the proportion of objects and images. When shooting the same subject at the same distance, the image with long lens focal length is large, and the image with short lens focal length is small. According to different uses, the focal length of camera lens varies greatly, from a few millimeters to a dozen millimeters to several meters.

Generally speaking, the focal length we are talking about is the distance from the center of the lens to the focus. But this is only the case of a single thin lens. Because the lens of a camera is composed of many lenses, the situation is far from simple.

4. The focal length of the lens is divided into image focal length and object focal length. The focal length of an image is the distance from the main surface of the image to the focal point of the image, and the focal length of an object is the distance from the main surface of the object to the focal point of the object. It must be noted that the focal length of the object and the focal length of the image are not necessarily equal, because the telescope structure is widely used in camera lens design, especially zoom lens. What we usually call the focal length of the camera lens refers to the focal length of the image.

Question 8: What does the camera 3.6mm mean? Focal length, generally 3.6 mm 6 mm 8 mm12 mm16 mm, are the most commonly used angles and distances. The greater the angle, the closer the distance. 67.4 degrees for the 3.6mm lens, 42.3 degrees for the 15m 6mm lens, 32.6 degrees for the 20m 8mm lens and 22 degrees for the 25m 12mm lens.

Question 9: What does the focal length mean in a camera? In photography, the concepts of focal length and focal length are often confused.

As the above two people said, the distance from the midpoint of a lens or the theoretical point of a lens group to the focal plane (that is, film or photoreceptor) is the so-called "focal length", which is optically called the image distance (not the object distance mentioned upstairs).

The distance from the object to the midpoint mentioned above is the optical object distance. Under normal circumstances, the "focal length" should be called this object distance, but in order to use the distance from the focal plane to the object conveniently when marking the lens.

The actual function of focal length (the principle is omitted here, and you can check the encyclopedia if you are interested) is reflected in the lenses with different focal lengths, and the refraction angle of light is different, so the viewing angle reflected in the photos is also different. The shorter the focal length, the wider the viewing angle, the longer the focal length and the narrower the viewing angle.

In addition, if the size of the subject remains the same, the perspective effect of the lens with different focal lengths is different. Because of the wide viewing angle, the lens with the focal length needs to be closer to the subject, and the object behind it will appear smaller and farther away from the subject. On the contrary, the telephoto lens needs to be farther away from the subject because of its narrow viewing angle, in order to obtain the subject of the same size, and the thing behind the subject will be bigger and look closer to the subject. This detailed truth needs drawing to illustrate, so I won't elaborate on it. I tried it a few times before I realized it.

Question 10: How to choose the focal length of the surveillance camera? When selecting targets in the monitoring room and other environments, small-scale monitoring is often the main method, and lenses with relatively close focal length need to be configured. Otherwise, too far focal length can not only improve visual clarity, but also cause weakness because of out-of-focus Generally, in the monitoring environment of ordinary conference rooms, offices and elevators, a close-range fixed-focus lens of about 3mm to 12mm can meet the demand. For residential security monitoring or ordinary road monitoring, the monitoring lens from 6mm to 15mm can basically meet the demand. For general intersection monitoring, because of the large shooting space and high definition requirements, it is suitable for a medium-distance focal length lens of 6mm to 60 mm. For the camera lens used for urban public security monitoring, because of the different monitoring distance and environment, it is basically enough to configure a long-distance zoom lens of about 10mm to120 mm. Finally, it is used for highways, national highways, rivers, airports, forests and other large areas. In these environments, the monitoring range is far the main feature of these environments, so the lens in the range of 10mm to 1 100mm is generally selected to meet the shooting requirements. In addition, in the imaging characteristics of the lens, the larger the focal length, the farther the monitoring, but the smaller the observation angle; The smaller the focal length, the closer the monitoring distance and the larger the field of view angle, so this is a contradictory relationship, and only the distance and angle can be selected. So when choosing the focal length, it is often measured according to the shooting angle. However, too large or too small initial focal length may have some adverse effects on the monitoring effect.