Providing a clear, colour image to aid in recognition and identification of objects, even in low-light, has seen analogue cameras lose their last advantage over IP cameras. This article will look into the following factors that lead to obtaining high image quality; reliable installation, seeing in the dark and providing good images where there is a contrast between light and dark.

Tunnels are bottlenecks in the traffic system: often humid, dirty and with typically very cramped environments. Installation of cameras needs to be very quick to minimise the disruption of traffic and the time installers spend in potentially dangerous environments. On the other hand, a camera needs to be carefully mounted and configured to deliver to its full image quality potential. It is vital to work with technology that can be installed in a matter of minutes. In an ideal scenario, a camera’s technology will allow a lot of the configuration to be done outside the tunnel or even from the comfort of a control centre: this includes remote zoom to select the right field of view, remote focus to set sharpness and pixel counter to ensure optimum resolution.

Naturally, tunnels can be very dark environments. It is often not economical, or even possible, to have bright lights in tunnels, which is what many cameras need to deliver good image quality. Surveillance cameras traditionally switch to black and white when light drops below a certain level. Axis’ Lightfinder technology however delivers good quality color images, even in very low light situations. This is ideal for security installations that require colour for recognition and identification. The noise reduction of the Lightfinder technology is vastly improved compared to the analogue cameras on the market, which in combination with the light sensitivity of the sensor gives a superior image quality with smooth, clear video of moving objects, surpassing any advantage analogue cameras had.

In other instances, it is more useful to complement the cameras with infrared (IR) lights. IR lights require no light at all in the tunnel to work, and even though a camera with IR lights only delivers black-and-white pictures, the pictures can offer great contrast and very low noise. If the camera needs to see over long distances in darkness, a thermal network camera could be a better choice; it typically delivers less detail than a traditional camera, but can detect people and other objects from great distances of several kilometres away.

Sometimes, it is not the darkness that is the problem, but the contrast between dark and light areas. Many cameras struggle to deliver good images in situations with strong backlight or a lot of reflections. This is a common problem in tunnels, where tunnel openings are very bright while the tunnel walls are dark. A similar situation appears for example when a train approaches with strong headlights inside a tunnel. Most cameras cannot handle these great differences in light levels and as they try to compensate for the strong light in one part of the scene, other parts will become dark, blocking out any image details. Axis offers cameras with wide dynamic range (WDR) that are designed to handle a high range of light levels in one single image, ensuring that details are visible both in dark and light areas of the monitored situation.
 
The use of the latest sensor technology and continual development of smarter software will continue to improve product development on the low-light application market.

Wai King Wong is Country Manager Australia and New Zealand for Axis Communications. Wai King is responsible for the management of all sales and operational activities in ANZ and has held the position since November 2002.

Wai King joined Axis Communications following a three year stint as senior product manager – Networking and Support Services Manager (Malaysia) Technical Consultant (Australia) at Ingram Micro.

Wai King has extensive knowledge and experience in the networking and software deployment and support arenas and holds a bachelor of Business in Business Information Systems from the Royal Melbourne Institute of Technology (RMIT) and a Master in Business and Technology, UNSW.

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