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Figure 4 - All video cameras will have connectors for power and video output
Figure 4 - All video cameras will have connectors for power and video output

Security cameras and micro spy cameras will have a connection point for DC (direct current) power and a video output, and some will have an audio output or several control lines for onboard features such as gain, color, text overlay, and lens control. The most basic cameras you will probably work with most often will have only power and video connectors, or simply include three wires coming out of the tiny enclosure. The tiny board cameras with three wires will usually follow a simply color scheme of black or green = ground, red = positive power, and white, yellow or brown = composite video output. Of course, it is always a good idea to check the manual for polarity and voltage before making any guesses.

The camera in the left of Figure 4 is quite advanced, having a built in on screen display system, many internal function parameters, lens control, and audio. This camera is somewhat large, so it has many buttons on the back side, audio and video jacks, DC power jack, and a special connector to control a motorized lens. The basic low lux micro camera on the right of Figure 4 only has a tiny connector with a three wire cable to allow power, ground, and video output connections. Since you will be powering the camera from a battery source, the smaller camera will be the better choice.



Figure 5 - The CCD imager makes video by changing light into an analog voltage
Figure 5 - The CCD imager makes video by changing light into an analog voltage

When digging into the technical details of a security camera, one of the most important aspects will be the type of imaging device used, which will either be a CCD imager (charge coupled device) or CMOS imager (complementary metal oxide semiconductor). Both types of imagers convert light into voltage and process it into electronic signals. In a CCD sensor like the one shown in Figure 5, every pixel is transferred through a very limited number of output nodes (often just one) to be converted to voltage, buffered, and sent off-chip as an analog signal. All of the pixels can be devoted to light capture, and the image quality is high. In a CMOS sensor, each pixel has its own charge-to-voltage conversion, and the sensor often also includes amplifiers, noise-correction, and digitization circuits, so that the chip outputs digital bits. These other functions increase the design complexity and reduce the area available for light capture.

What this means is that for low resolution and low light imaging, CCD cameras are currently the best choice. CMOS imagers are used in very high resolution imaging systems such as digital cameras and scanners as proper lighting is usually not a problem. If you have the choice between a $100 CCD security camera with a .5 lux rating and a $50 CMOS camera with a 1.5 lux rating, the CCD camera will offer a far superior image and work well in a low light or night vision application. Resolution is not much concern in a security camera, as most are already beyond the actual capabilities of the NTSC (National Television System Committee) or PAL (Phase Alternate Line) composite video standard anyhow. The Lux rating will probably be the most important specification on a security camera next to the type of lens and field of view.

Lux is the measure of light or luminous power per area. It is used in photography as a measure of the intensity, as perceived by the human eye. The lower the Lux rating on a camera, the better it will see in the dark. For instance, a monochrome camera with a Lux rating of only .5 lux will see much better in the dark than you could with your naked eye, and with the help of an infrared illuminator will be able to see into the darkness and display it on a monitor as if it were mid day. Color cameras require much more light to achieve a decent image, and since they usually include infrared filters, they are not the best choice for night vision applications.

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