2. Scene analysis

Once you have defined your overall goals, determine the requirements for individual cameras for each application. In addition to the level of detail, consider:

• Area of coverage: How many ‘interest’ areas need to be covered for a given location. Are they located close together, or far apart? This decides type and number of cameras needed.
• Lighting conditions: Most network cameras offer day and night functionality, with some limitations. Is lighting restricted? Is artificial lighting possible?
• Indoor or outdoor installation: Ambient light levels may require you to consider day-and-night cameras, or extra lighting equipment, as well as housings that protect cameras against dust, humidity and vandalism. These are critical considerations for outdoor cameras, but can also affect indoor cameras.
• Overt or covert surveillance: Clearly visible surveillance cameras can be effective deterrents against potential miscreants, but they can also invite vandalism. Choosing discrete or non-discrete installation affects your selection of cameras, as well as housings and mounts.

3. Camera selection

The cameras you choose are the major step to completely satisfactory fulfillment of your video surveillance goals. Take time to understand this complex subject area, in order to make the best-informed camera choice.

Image resolution is a critical technical feature of any network camera, and the one that has received the most ‘buzz’ in the past couple of years. From this perspective, there are essentially three categories of network cameras: megapixel, HDTV (high-definition television) and standard resolution (analogue CCTV cameras connected via video encoders fit into this last category too).

Megapixel network cameras are an adaptation of industry best practice, but do not follow any standard. The ‘number’ of megapixels refers specifically to the number of image sensor elements in the camera. Megapixel network cameras can provide extreme image detail, but often at a lower frame rate, and some can even deliver different video streams from different areas of the same image. Good megapixel applications include overview surveillance in banks, transportation hubs and other premises.

HDTV network cameras deliver a pleasing image, with full frame-rate, excellent colour representation and wide-screen (16:9) format. True HDTV cameras fulfill key parts of industry standards such as SMPTE. HDTV is ideal when full frame rate is needed – for airports, casinos, city surveillance and passport controls.

Standard resolution is usually VGA (640 x 480 pixels) or a multiple of it, and is the ‘oldest’ category in the network video surveillance camera market. But its use is still both current and valid: with a powerful optical zoom, a VGA camera fully answers many monitoring needs; in difficult lighting, a VGA camera with extreme light sensitivity and wide dynamic range can outperform both HDTV and megapixel cameras; some VGA cameras provide frame rates higher than 25-30 frames per second – perfect for capturing fast-moving objects.

Regardless of category, the following factors are critical, and need to be considered when choosing a camera:

• Frame rate – 25-30 frames per second (fps) are the PAL and NTSC standards. Unless an event occurs, 1-4 fps is usually enough for recording purposes
• Optics and lens elements – the lens defines field of view, limits light reaching the sensor, and focuses the camera, deciding image quality and supporting the camera’s range of surveillance capability
• Light sensitivity – Measure the scene’s luminance under a range of lighting conditions, and then test the camera carefully to make sure it meets your light sensitivity needs.
• WDR (Wide Dynamic Range) – WDR makes it possible to handle a wide range of lighting conditions in one scene, by using different exposures for different areas of the same image.
• Noise reduction – ‘Noise’ can come from the light source, or from sources including the image sensor and other electronic camera components.
• Iris control – This is important to image quality. It can be fixed or adjustable. Adjustable-iris lenses can be manual or automatic.
• Video compression – This reduces file size and promotes efficient transmission and storage. Make sure standardised compression techniques are employed, to ensure compatibility and interoperability.
• Scanning technique – Today, there are two techniques used to read and display video information: interlaced- and progressive scanning. The latter is preferable, as it minimises ‘motion blur’.

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