FAQ of security camera CCD Sensor, resolution, Sensitivity, Lens
Now all the professional type cameras are CCD (Charged Coupled Device “in Castilian, charge-coupled device), and within these chips are not all equal, there are different sizes, the most common are 1 / 4″ 1 / 3 “, 1 / 2″ and 1 “in the type of image that will attract, the bigger the chip the greater the image quality to be obtained. The cameras are more common 1 / 3 “, and the image depends on the lens is placed.
ie the number of horizontal and vertical lines are used to form the image, gral. ranging between 380 and 420 lines and high-resolution cameras between 500 and 570 lines. But how to know which camera to use, that depends on the design of your system, of which we spoke above, but you could say that the larger outdoor camera resolution image to get better because we use lower-angle lens and more powerful (these allow less light to pass that wide angle) and also because the use of night and therefore we will have less light, indoor situations change we can use medium-resolution cameras because they use wider angle lenses and our lighting gral . will always be family. It is important to evaluate which is the condition for security, the system used to monitor or record and play only if an event warrants. In the first case, if you put a camera of 570 lines of resolution on a monitor 5 “400 lines, the image only has 400 lines, ie the resolution of the monitor, if instead you place a resolution of 380 lines in a 15 “monitor and 1000 lines have only 380 image lines, ie the resolution of the camera, this is a good reason not to put conventional televisions because they never exceed the 325 lines of resolution. Now the whole system needs to burn to use the recording in case of an event, place a camera of 570 lines, a monitor 1000, and a time-lapse VCR of 330 lines of resolution in the reproduction is 330 lines , ie the video, even when monitoring is of high quality
This is measured in lux, the lower the amount you work, the greater the sensitivity of this. However, it is a lux is the amount of light that is measured in a square foot to light 10 candles to 30 cm. it, today’s cameras ranging from 2 lux and 0.04 lux, ie a camera with 0.1 lux could do with some sharpening to 30 cm. with the light of a candle. As we know light is reflected and that we must take into account when making a design and choose the camera is not the same watch a night with the black asphalt to the same place covered by snow, they have different refractory and therefore different light. This theme of light is sometimes not taken such an account as it should for installers and yet it is one of the first things you need to evaluate not forget the camera’s similarity to the human eye without light see anything. In a dimly lit, and a conventional camera sensitivity will produce a dark, muddy image that probably displeased customer.
help the installer to solve problems that can occur in a work, the two most important and worthy of mention are the autoshutter (electronic shutter) and back-light controller (light background). The first is a kind of flicker that makes the camera, the more light there is, the faster the flash, and the less light there, blinking more slowly, when it comes auto shutter of 1 / 100000, that means that the CCD can sample the amount of light (flashes) up to 100000 times a second. Well, now with this criterion does not require iris lens, wrongly, certain changes in light or reflected light that can not be corrected if there is an auto iris lens. The second is a camera function that solves a large part (not 100% solution) the problem presented by an object or a person against a bright light in the background, this figure is only a silhouette on a light background, This is because the lens iris or camera autoshutter working on more light, and close or blink more quickly to adapt to it, leaving the figure in the dark, which makes back-light controller is to compensate for these two images, the very clear and very dark, and instead of adapting to the increased amount of light leaving out an average a little more clear the background but also becoming more clear and visible figure.
Intelligent Electronic Domes:
these cameras combine electronics with mechanical CCD zoom and movement of the “pan-tilt.” It operated from a joystick controller are shown in dark hemispheres to hide the camera and go unnoticed. Its use is common in large venues such as shopping centers, warehouses, supermarkets, etc. The main advantage of these devices is the speed with which they move and therefore can track the movements of an operator, on the other hand have a number of pre-programmable positions that make the camera is set at certain points automatically and in turn these positions may be related to certain alarm events, for example, installed a dome on a deposit of goods in a hypermarket that is controlling all internal movements but to open the gate to the outside, it triggers a sensor, and automatically searches for a set position and moves toward it.
Yet another common use is to control the country's perimeters, in the same way if a violation at some point on the dome moves the camera to the preset position and associated with that point. Color or Black and White, many times the installer asks this question and as many times the price gives the answer, but it is not unique. True color cameras are more expensive than black and white, but are gradually lowering its price and in some years there will be much more expensive than the others, on the other hand the more you sell, but lower their costs. But as said price is not everything, the camera resolution b / n is higher than the color (there are about 100 lines average difference) and the other issue is the sensitivity in the color that is less than in the b / n, which means you need more lighting in the place were installed.
The other issue with the color and light, is that the latter according to the type that is (day, fluorescent, tungsten, mercury, etc.) Has a different temperature and this gives a different color, so it should be careful again with the location of the cameras. Now no doubt allow the identification color cameras is not comparable in any way with the view offered by the b / n, for example, as was the person, blonde, who wore T-shirt color, the person is entering dress-coat color that corresponds, etc.
these eyes of the camera and depends on the measure used will get an angle and a different viewing distance. According to the CCD camera has the lens type to be used, eg., For a camera of a 1 / 3 “lens should also use a 1 / 3″ but we get a ring around image. Comparing a lens with our eyes, with a camera of a 1 / 3 “mounted on the shoulders and an 8mm lens. you get the same image our eyes. The following table shows the area covered by a lens of 1 / 3 “to 10 feet away:
Lens Horizontal Vertical
2,8 17.1 m 12.9 m
4 12 mts 9 m.
6 8 m. 6 mts
8 6 mts 4.5 m.
12 4 m 3 mts
16 3 mts 2.3 m
There are also lenses that have several steps, these are called varifocal, can take the same lens different sizes and angles by simply moving a ring by hand, the most common is 3.5-8mm. Another type of zoom lens is the motor that goes from wide angle to telephoto or normal with a motor that moves the lens and remote control, now and know when to use these lenses, if we have to control a where we have to look to places near and far distances, is in case where its use is recommended. The most common these are 4-48mm lens or 8-80mm.
this name has a lot to do with our eyes, as in these the iris opens or closes to let more or less light as needed, in photography is called diaphragm and performs the same function. There are three types of iris: fixed, manual and auto iris. The first always has the same opening and is recommended in an enclosed area and always have the same lighting conditions, in the second mechanical handling of the iris is as its name implies manual, and it will vary accordingly as conditions change light, however if they change constantly and the lens is out of reach this is not the lens to use, for these circumstances should be used iris lenses.
These lenses automatically handle the opening and closing the iris, with the use of electronics that can be found in the lens or camera, according to this is that they are known or assets, and DV video or passive, direct or DD. Well now as they do to know when opened or closed, measure the video level should always be 1Vpp, ie if there are many video light level rises above this measure then closes the lens iris, if change in low light level video is below 1Vpp and opens the lens iris. According to the opening of iris obtained will have a different depth of field, though this is the distance between those that were in focus images, a greater depth of field smaller aperture opening smaller and greater depth of field, ie during the day will focus distances and at night they will be short. Another factor that weighs the lens is far more depth to a lesser extent and less depth further.
It’s really important to get a good approach and that is why all the cameras have a way of delaying or advancing the CCD to get perfect focus. Another feature of the lens is the focal aperture or f-stop and they indicate the maximum aperture you can get the lens, the f-stop numbers are, the smaller these greater the aperture, the higher the number the lower opening . These numbers are always following the extent of the lens and are, f1-4, f-2, f-2.8, f-4, f-5.6, f-8, f-11, f-16 and F-22.
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Tags: CCTV Cameras