Monitor the main points of the camera, whether you buy or debug surveillance cameras, you should understand the four main points of surveillance cameras: maximum aperture, focal length, close-up ability, expressiveness.
The true value of the maximum aperture is achieved by increasing the amount of light in the case of low light so as to achieve the optimum exposure combination. Shooting scenery generally does not require the lens of virtual ability, in addition to the exception of particularly dark places, generally not too demanding lens caliber. However, when the 70 - 200mm zoom lens is fitted with a 2 zoom lens and the zoom section becomes 400mm and the AF autofocus is used, it is best to select the lens with the maximum aperture of F2.8. The large aperture facilitates accurate focusing in darker conditions. Using large bore lenses to shoot people, even in weaker places, the handheld can take advantage of natural light. In addition, the maximum aperture lens can bring faster shutter speed, so sports photography also requires large aperture lens.
Another reason for a large lens aperture is the ability to blur the background freely and ensure virtual quality. Maximum aperture F1.4 of the lens, when the aperture is reduced to F2, whether the imaging quality or the virtual quality of the background is better than the maximum aperture is F2 lens. So, a large aperture lens reduces the aperture of one lens and has considerable value. Any photographer should be good at using the lens.
Two focal length
The first thing we should pay attention to is the focal length of the lens. The focal length is actually the angle of view. The focal length is different and the angle of view is different. In addition, the user himself must be clear, what is the main purpose of my purchase of the lens? Is it for the scenery or for the characters?. As we all know, the scenery should be shot with a wide-angle lens, and the characters should use a telephoto lens, so first of all, according to the purpose of photography to determine the focal length of the lens that you want to buy.
The best focal points for shooting landscapes are the wide-angle focal section 24mm and the telescopic focus section 200mm (both in the 35mm standard and the same below). When the standard zoom lens has a wide-angle focal section from 28mm to 24mm, the angle of view becomes larger, and the range of view can be greatly widened. Generally speaking, the maximum aperture required for shooting scenery is not very high. If the main landscape, then choose zoom lens, wide-angle focal section is 24mm, basically enough. As far as the zoom section is concerned, at least 200mm, if the telescope focus is 300mm or 400mm, will be more ideal, and the freedom will be greatly improved. Traditional zoom lens telescope focus section is 300mm, used in digital SLR is 450mm, focal length expanded by 1.5 times, use it will make people feel more happy, this is exactly the value of digital slr. Now produced digital special ultra wide-angle lens wide-angle focal length to 12mm, equivalent to 35mm specifications 18mm, 28mm than 35mm focal length specifications of nearly 1.5 times larger, so that the scenery around shooting scenes greatly widened the scope of.
The best focus for shooting characters is 85mm. In terms of 35mm specifications, the shot character basically selects the lens with the 85mm focal length as the standard. 85mm focal length portrait taken close to medium format camera picture effect, not only the appropriate sense of distance, but the face is very natural, camera and basic figures were taken between the distance can be maintained at a normal speaking distance. 85mm focus is also a good way to blur the background and highlight the characters. In order to obtain a good virtual effect, it is better to choose the lens with the largest aperture. 85mm focus on the digital SLR is about 135mm, although the picture appears to be a little weak near and far, but basically nothing serious, so the focus of shooting characters lens at least about 85mm.
Take flowers to have a traditional SLR 100mm macro lens is enough. 100mm macro lens can be such as photography, can shoot flowers heavily, but other times, when photography or near times photography, because the king long focal depth, prone to jitter, so the shooting should be considered anti shake measures. From this point of view, the 50mm macro lens used in digital SLR is more easy to use.
Three 、 near shooting ability
The camera's near camera ability is another focal point after the focal length and the maximum aperture. This is the same for wide-angle lenses, standard lenses, or telephoto lenses. So, how close ability is appropriate?
First, wide angle lens landscape, close up almost no relationship to what the ability of wide-angle lens, but when shooting with a broad background of landscape flower scenery, often to the flower looks a bit bigger, in similar circumstances the wide-angle lens close-up ability is very important.
The existing 50mm standard lens near shooting ability is about 45cm, basically meet the use. However, when large lenses are used in the shortest distance, there is often a greater aberration due to the lens extension, which makes the image quality poor.
If the telephoto lens is used for shooting the scenery, there is no great demand for the near shooting ability. However, the ability to take close-up shots of a shot is very important if it is used to photograph people or flowers.
Four, expressive force
When choosing lenses, many people first notice how sharp the lens is. The use of photos determines the sharpness of the lenses. High quality lenses are mainly used by professional photographers, and if it's just general photography, there's no need to spend a lot of money on expensive quality lenses. In addition, the sharpness of the lens is directly related to the size of the aperture. When a lens is reduced from one or two to the maximum aperture, the sharpness of the image will be greatly improved.
Distortion is an optical phenomenon caused by the optical properties of the lens. It is impossible for each lens to be free of distortion. The manufacturer has corrected the distortion during the production of the lens and tried to minimize the distortion. There are three main types: General lens distortion pincushion distortion barrel distortion, telephoto zoom lens wide-angle end is prone to end prone and bamboo hat type distortion generated by modifying the barrel distortion of the wide-angle end. As far as the current lens situation is concerned, the most prominent problem is the barrel shape distortion at the wide angle end, so it is possible to choose the small distortion style as far as possible.
Backlight photography due to strong sunlight or other strong light source in the mirror reflected will form a halo and flare on the screen. This small part of the flare and flare will not only be imaged on the screen, but will also form reflections in the mirror and degrade the image quality. In order to prevent this phenomenon, the backlight photography must use hood. Excellent shot in the manufacturing process to completely prevent the process of halo and flare, even in contrast to backlit film is also very good. The classification of surveillance cameras depends on the color of the image:
(1) color camera: suitable for identifying the details of the scene, such as identifying the colors of clothing or scenery. The amount of information is increased by color, and the amount of information is generally considered to be 10 times that of a black-and-white camera.
(2): black and white camera is used for low light and night lighting equipment can not be installed in the area, the scenery only monitor the position or movement, can use black and white camera resolution is usually higher than the color camera.
Divide by camera resolution:
(1) the image pixels are around 250 thousand pixels (pixel), the color resolution is 330 lines, and the black and white resolution is about 420 lines.
(2) the mid-range type image pixels in 250 thousand between ~38 million, 420 line, black and white color resolution resolution on the line 500 (3) of the image in the above 380 thousand points, the color resolution is greater than or equal to 480, the black and white line resolution, high resolution more than 570 line.
Camera sensitivity division:
(1) general type: the normal work required illumination is 1~3Lux
(2) moonlight type: the illuminance required for normal work is about 0.1 Lux
(3) starlight type: the illuminance required for normal work is below 0.01 Lux
(4) infrared lighting type: in principle, it can be zero illumination and infrared light imaging.
The size of the CCD target surface is divided according to the imaging element:
(1) l inch target surface size is wide, 12.7mmX high 9.6mm, diagonal 16mm
(2) the 2/3inch target surface is wide, 8.8mmX high, 6.6mm, diagonal 11mm
(3) the 1/2inch target surface is wide, 6.4mmX high, 4.8mm, diagonal 8mm
(4) the 1/3inch target surface is wide, 4.8mmX high, 3.6mm, diagonal 6mm
(5) the 1/4inch target surface is wide, 3.2mmX high, 2.4mm, diagonal 4mm
(6) 1/5inch is under development and has not yet introduced the installation method of a formal product installation monitoring camera
1) come up with support, ready tools and parts: up plug, screw, screwdriver, hammer, electric drill and other necessary tools; according to the installation location determined beforehand, check up the plug and tapping screw sizes, try and camera bracket screw base screw is appropriate, whether the pre buried pipeline interfaces handle the test cable, is smooth, ready to enter setup.
2) out of the camera, the camera lens according to predetermined types and specifications, carefully mount the lens (integrated infrared camera does not need to install the camera), be careful not to touch the lens and CCD by hand (labeling map), confirm the fixation after the power is switched on, communicated with the main machine or field use small TV monitor, etc. adjust the aperture and focal length.
3) took up support, plug, screw, screwdrivers, hammers, drills and other tools, according to predetermined position, install bracket. After checking firmly, place the camera in the agreed direction;
4) if you need to install the shield, start the installation shield directly from here after the second step. 1, open the protective cover and the baffle; 2, out of a fixed metal sheet, the camera is fixed; 3, the power adapter into the inside of the shield; 4, the reduction of the cover and the baffle, straighten out the cable, fixed, mounted to the bracket.
5) plug in the video cable BNC plug into the socket of the video cable, and make sure it is firmly fixed.
6) plug the power output plug of the power adapter into the power jack of the monitoring camera and confirm the fastness.
7) connect the other end of the cable to the control host or monitor (TV) to make sure it is solid.
8) monitor the host and camera power, adjust the camera angle to the preset range through the monitor
Attention should be paid to the installation of surveillance cameras. 1) in the conditions to meet the surveillance target field of view requirements, the installation height: indoor ground should not be less than 2.5m; outdoor ground should not be less than 3.5m.
2) surveillance cameras and their supporting devices, such as lenses, shields, stents, wipers, etc., should be installed firmly, the operation should be flexible, attention should be paid to prevent damage and coordination with the surrounding environment.
3) in the strong electromagnetic interference environment, the monitoring camera should be insulated from the ground.
4) signal wire and power line should be introduced separately, the exposed part is protected by hose, and it does not affect the rotation of the pan head.
5) the monitoring camera in the elevator cabin should be installed on the left or right side of the overhead door, and it can effectively monitor the occupant's facial features in the elevator cabin.
6) the installation position of the console and cabinet (cabinet) shall comply with the design requirements, and the installation shall be stable and easy to operate and maintain. The distance between the back and the side of the rack should be in line with the maintenance requirements.
7) monitor the camera, all control, display, recording and other terminal equipment installation should be smooth, easy to operate. Among them, the monitor (screen) should avoid foreign direct light, and when unavoidable, light avoidance measures should be taken. The equipment installed in the console and cabinet shall have ventilation and heat dissipation measures, and the internal connector shall be connected with the equipment securely.