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The emergence of high-definition video camera security system brings picture quality greatly improved, such as 720p, 1080p's HD ip cameras, 3M, 5M high resolution industrial cameras. Ancillary HD lenses on the market also appeared in large numbers, but the actual use of many problems discovered after the market is flooded with a variety of different quality. Have sufficient resolution as an ordinary resolution, there is uneven clarity, the central part of the lens to achieve the required resolution, edge resolution is poor, etc., the actual application is not optimistic. For security systems, especially in the field of road surveillance applications requiring wide angle lens can have a range of high resolution (eg with 1080p HD ip camera with the lens resolution requires more than 2M), simply, is the lens MTF curves have higher requirements. Meanwhile, in order to fully reflect the characteristics of the camera's low light, the lens should have the amount of light Chase (F value is smaller). MTF of the lens can be used to analyze and judge the image quality of a lens. The value of MTF (modulation transfer function) is the lens sharpness, contrast and resolution comprehensive evaluation value. Of course the lens MTF value is not universal, it does not show the lens chromatic aberration, dispersion, field curvature, etc., so the lens can not explain everything, but it really is the performance of the lens optical capabilities at this stage the most scientific, the most comprehensive index. Aperture relative aperture F value is the reciprocal of light through the lens relative aperture diameter divided by the focal length of the lens resulting relative value. F-value is a measure of the amount of light the lens is an important reference index, the smaller the aperture F value factor, in the same unit of time the amount of light it the more. In general, monitoring systems, especially road monitoring system, the illumination varies greatly throughout the day, in the first guarantee F8 aperture lens has a better image quality, the remote monitoring for night shots, the F-value requirements small enough to ensure a relatively large aperture state, a good image quality. Of course, the smaller the F value, the more expensive the price of the lens, the case of large multiple zoom lens, the lens price is much higher than prices in other parts of the camera. While on the road monitoring system, especially in urban road monitoring day and night in the optional dual-purpose lens, in addition to the lens aperture values, but also considering the lighting conditions to infrared light amended to ensure a clear image. Outdoor surveillance system due to illumination changes, generally require the use of auto-iris lens. Of course, the actual amount of light through the lens, in addition to the F value in addition to other factors, such as coating, the lens material and the size of the lens itself. We have found the same in the test F value, the actual amount of light will be a difference of 20%. Integrated optical performance of these lenses, as well as the special requirements of monitoring system, which requires a relatively large aperture, the lens MTF to high-quality,HD ip cameras can accurately reflect the performance of HD lenses for material selection, manufacturing processes, etc. have very high requirements. According to the comprehensive lens on the market price, we recommend manual zoom lens F-value of 1.2 to 1.4, motorized zoom lens F value of 1.6 to 1.8. So as to maximize the camera's low light performance reflects. Network cameras are usually divided into two types: one is based on the preceding video and analog cameras into network processing module, analog cameras have the same drawbacks: the image resolution is not high, the highest quality of not more than D1, another digital HD network camera, which is characterized by a direct digital video processing and transmission via the network, to avoid the common problem of analog cameras vulnerable to interference, you can do the screen clean, crisp and clear picture quality, signal to noise ratio is high. To make megapixels ip camera can get the best performance, use high quality megapixels lens will be very important. Optical image quality is the overall image quality is a key factor, as HD network camera "eyeball" megapixels ip camera for the entire image with high contrast, sharpness and clear sharpness, rather than megapixels ip camera can not fully demonstrated megapixels sensor resolution, especially in the edge of the picture. CCD and CMOS is by using the pixels arranged in a two-dimensional grid, the pixels of the optical image is converted into an electrical signal. A number of pixels on the image usually determines the resolution of the image, more pixels means a higher resolution. Compared to ordinary lenses, megapixels ip camera on monitor screen shows images more delicate, detail section to show a good image will not appear blurred. When choosing megapixels ip camera image plane to the attention of the lens size and the size of matching SENSOR physiognomy, CCTV cameras have a variety of different sizes of the sensor, the screen aspect ratio is usually 4:3 (horizontal width: vertical height) or 16:9. The size of the sensor field of view angle of impact, the use of the same lens in a smaller angle of view of the sensor is more narrow, and selection of different functions depending on the application of megapixels ip camera, such as the illumination optical lens Cosmos, ultra-wide-angle lens non-IR lens, IR lens, through the fog lens, autofocus lens, FA prime lenses and fisheye.
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