[ Pacific Security Network News
Ask everyone a question, what is the relationship between camera lens and distance? Do you know? When an object is in focus, all scenes from a certain distance in front of the object to a certain distance behind it are also clear. The distance from front to back with a fairly clear focus is called depth of field. The depth of field is divided into deep foreground and deep depth of field, and the depth of the back is deeper than the foreground. The deeper the depth of field, the more distant the scene can be clear, and the depth of field is shallow, the scene far from the focus is blurred.
The following section of the Pacific Security Network is a detailed introduction to the relationship between camera lens and distance.
On the left is the lens. On the right is how far is the photo.
Lens focal length optimal distance viewing angle 3.6mm (super wide angle): 1 ~ 3 meters 92 degrees 4mm (super wide angle): 3 ~ 5 meters 74 degrees 6mm (standard 1): 5 ~ 8 meters 55 degrees 8mm (standard 2) : 8 ~ 10 meters 34 degrees 12mm (telephoto): 10 ~ 12 meters 23 degrees 16mm (telephoto): 12 ~ 15 meters 17 degrees
Standard lens: The viewing angle is about 30 degrees. In the 1/2-inch CCD camera, the standard lens focal length is set to 12mm. In the 1/3-inch CCD camera, the standard lens focal length is set to 8mm.
Wide-angle lens: The viewing angle is more than 90 degrees, and the focal length can be less than a few millimeters, providing a wide viewing angle.
Telephoto lens: The angle of view is less than 20 degrees, and the focal length can reach several meters or even tens of meters. This lens can enlarge the influence of the captured object at a long distance, but make the observation range smaller.
How wide is the focal length lens?
Lens focal length with 1/3" CCD with 1/4" CCD difference between the opposite sex
2.8 mm 89.9Â° 75.6Â° 14.3Â°
3.6 mm 75.7Â° 62.2Â° 13.5Â°
4 mm 69.9Â° 57.0Â° 12.9Â°
6 mm 50.0Â° 39.8Â° 10.2Â°
8 mm 38.5Â° 30.4Â° 8.1Â°
12 mm 26.2Â° 20.5Â° 5.7Â°
16 mm 19.8Â° 15.4Â° 4.4Â°
25 mm 10.6Â° 8.3Â° 2.3Â°
60 mm 5.3Â° 4.1Â° 1.2Â°
Second, can a 1/3" CCD lens finish the target?
Lens focal length
(mm) distance 5 meters
(width Ã— height) distance 10 meters
(width Ã— height) distance 15 meters
(width Ã— height) distance 20 meters
(width Ã— height) distance 30 meters
(width Ã— height)
2.8mm 13Ã—9.8 meters 26Ã—19.5 meters 39Ã—29.3 meters 52Ã—39 meters 78Ã—58.5 meters
3.6mm 8.5Ã—6.4 meters 17Ã—12.8 meters 25.5Ã—19 meters 34Ã—25.5 meters 51Ã—38.3 meters
4mm 8Ã—6 meters 16Ã—12 meters 24Ã—18 meters 32Ã—24 meters 48Ã—36 meters
6mm 5.5Ã—4.1 meters 11Ã—8.3 meters 16.5Ã—12.4 meters 22Ã—16.5 meters 33Ã—24.8 meters
8mm 3.5Ã—2.6 meters 7Ã—5.3 meters 10.5Ã—7.9 meters 14Ã—10.5 meters 21Ã—15.8 meters
12mm 2 Ã— 1.5 meters 4 Ã— 3 meters 6 Ã— Ã— 4.5 meters 8 Ã— 6 meters 12 Ã— 9 meters
16mm 1.5Ã—1.1 meters 3Ã—2.3 meters 4.5Ã—3.4 meters 6Ã—4.5 meters 9Ã—6.8 meters
25mm 1.3Ã—1 m 2.5Ã—1.9 m 3.8Ã—2.9 m 5Ã—3.8 m 7.5Ã—5.6 m
60mm 0.5Ã—0.4m 1Ã—0.75m 1.5Ã—1.1m 2Ã—1.5m 3Ã—2.3m
Third, 1/3" CCD lens can see how many meters?
3.6MM, 6MM, 8MM, 12MM, 16MM, 25MM multiplied by 2.4 is the farthest distance
Type of lens
There are many types of lenses, each of which has its own characteristics. Depending on the function and structure, the price of these lenses is very different. For example, the power zoom lens is about 10 times higher than the price of a normal fixed-focus lens. Therefore, the lens can be selected more flexibly only if the characteristics of various lenses are correctly understood.
A, fixed aperture fixed focus lens
Fixed-aperture fixed-focus lens is a relatively simple type of lens. There is only one manually adjustable focus adjustment ring (the ring is marked with a number of distance reference values). Rotating the ring left and right can make it on the CCD target surface. The image is the clearest, and the image on the monitor screen is also the clearest.
Since it is a fixed aperture lens, there is no aperture adjustment ring on the lens, which means that the aperture of the lens is not adjustable, so the luminous flux entering the lens cannot be changed by simply changing the lens factor, but can only be changed by the change. The illuminance of the scene is adjusted, such as increasing or decreasing the lighting of the scene. This type of lens is generally used in applications where the illuminance is relatively uniform, such as indoor lighting throughout the day, in other occasions, it is required to be used with CCD cameras with automatic electronic shutter function (of course, most of the current market) CCD cameras are equipped with an automatic electronic shutter function) that simulates changes in luminous flux through adjustment of the electronic shutter.
B, manual aperture fixed focus lens
The manual aperture fixed focus lens has a larger aperture adjustment ring than the fixed aperture fixed focus lens. The aperture adjustment range can generally be adjusted from F1. 2 or F1. 4 to fully closed, which can easily adapt to the illumination of the scene. However, due to the aperture The adjustment is manually performed manually. Once the camera is installed, the position is fixed, and it is not so easy to adjust the aperture frequently. Therefore, the lens is generally applied to the occasion where the illumination is relatively uniform, and in other occasions. It needs to be used with a CCD camera with automatic electronic shutter function. For example, in the morning and evening, when there is a large change in illuminance such as noon, sunny day and cloudy day, the change of the optical flux is simulated by the adjustment of the electronic shutter.
C, automatic aperture fixed focus lens
The auto-iris fixed-focus lens has a relatively large change in structure. It is equivalent to adding a micro-motor driven by a gear mesh to the aperture adjustment ring of the manual aperture fixed-focus lens, and extracting 3 cores or 4 from its drive circuit. The core wire is sent to the auto iris lens, so that the micro motor in the lens rotates in the forward or reverse direction, thereby the size of the high speed aperture. The auto iris lens is divided into two types: amplifier (video driven) and amplifierless (DC driven).
D, manual zoom lens
As the name implies, the focal length of the manual zoom lens is variable. It has a focal length adjustment ring that can adjust the focal length of the lens within a certain range. The ratio is generally 2 to 3 times, and the focal length is generally 3. 6 to 8 mm. In practical engineering applications, by manually adjusting the lens's zoom ring, you can easily select the field of view of the surveillance site, such as: you can choose to monitor the entire room or choose to monitor a local area of â€‹â€‹the room. When it is not well understood about the environmental conditions of the surveillance site, it is obviously very important to use such a lens.
For most TV monitoring system projects, it is very inconvenient to manually zoom after the camera is installed. Therefore, after the project is completed, the focal length of the manual zoom lens is rarely adjusted. To the role of the fixed focus lens. Therefore, the manual zoom lens is generally used in a situation where the demand is relatively strict and the fixed focus lens is not easy to meet the requirements. However, this type of lens is favored by engineers because it is used in the construction and debugging process. By adjusting the focal length within a certain range, it is generally possible to find a viewing range that can satisfy the user (without repeatedly changing the lens with different focal lengths). ), this is particularly convenient in field construction.
E, auto iris electric zoom lens
This type of lens additionally adds two micro motors to the aforementioned auto-iris fixed-focus lens, one of which is engaged with the zoom ring of the lens, and can change the focal length of the lens when it is controlled to rotate; the other motor Engages with the focus ring of the lens, and the focus of the lens is achieved when it is controlled to rotate. Since the lens adds two functions that can be adjusted remotely, this type of lens is also called an electric two-variable lens.
The auto-iris motorized zoom lens generally leads to two sets of multi-core wires, one of which is an auto-iris control line, the principle and connection of which are exactly the same as those of the aforementioned auto-iris fixed-focus lens; the other is to control the lens zoom and focus. The control line is generally connected to the pan/tilt lens controller and decoder. When operating the zoom or focus button of the remote control indoor pan/tilt lens controller and decoder, a positive or negative DC voltage will be applied to the zoom or focus control line, which is applied to the corresponding micro motor. , to complete the zoom and focus adjustment function of the lens.
Lens selection and main parameters
The camera lens is the most critical device of the video surveillance system. Its quality (indicator) advantage directly affects the camera's overall machine index. Therefore, whether the camera lens is properly selected is related to the system quality and the project cost.
The lens is equivalent to the lens of the human eye. If there is no lens, the human eye can not see any object; if there is no lens, then the image output by the camera; it is a piece of white, no clear image output, which is with our home camera and camera. The principle is the same.
When the muscles of the human eye are unable to stretch the lens to the normal position, which is often referred to as myopia, the scene in front of the scene becomes blurred; the cooperation between the camera and the lens is similar, when the image becomes unclear. You can adjust the back focus of the camera and change the distance between the CCD chip and the lens reference surface (equivalent to adjusting the position of the human eye lens) to make the blurred image clear.
It can be seen that the role of the lens in the closed-circuit monitoring system is very important. Engineering designers and construction personnel should always deal with the lens: the designer should calculate the focal length of the lens according to the object distance and imaging size. The construction personnel often perform on-site debugging, and part of it is to adjust the lens to the best state.
First, the classification of the lens
According to the shape function, divided by size, by aperture, by zoom type, by focal length and long moment:
*Spherical lens 1"25mm automatic aperture electric zoom, long focal length lens female aspherical lens 1/2" 3mm manual aperture manual zoom standard lens
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