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Advanced image features


When installing advanced network cameras, make sure all the camera’s image capabilities are put to use.


Day and night functionality


All types of network cameras —fixed, fixed dome, PTZ, and PTZ dome — can offer day and night functionality. A day and night camera is designed to be used in outdoor installations or in indoor environments with poor lighting.

A day and night, color network camera delivers color images during the day. As light diminishes below a certain level, the camera can automatically switch to night mode to make use of near infrared (IR) light to deliver high-quality, black and white images.

Near-infrared light, which spans from 700 nanometers (nm) up to about 1000 nm, is beyond what the human eye can see, but most camera sensors can detect it and make use of it. During the day, a day and night camera uses an IR-cut filter. IR light is filtered out so that it does not distort the colors of images as the human eye sees them. When the camera is in night (black and white) mode, the IR cut filter is removed, allowing the camera’s light sensitivity to reach down to 0.001 lux or lower.




Figure 6. Graph illustrating how an image sensor responds to visible and near-IR light. Near-IR light spans the 700 nm to 1000 nm range.



Figure 7. Image at left, IR cut filter in a day/night network camera; middle, position of IR-cut filter during daytime; at right, position of IR-cut filter during nighttime.

Day and night cameras are useful in environments that restrict the use of artificial light. They include low-light video surveillance situations, covert surveillance, and discreet applications, for example in a traffic surveillance situation where bright lights would disturb drivers at night.


Wide Dynamic Range (WDR)


Wide dynamic range is a feature that incorporates techniques for handling a wide range of lighting conditions in a scene.

In a scene with extremely bright and dark areas or in backlight situations where a person is in front of a bright window, a typical camera would produce an image where objects in the dark areas would hardly be visible. Wide dynamic range solves this by applying techniques such as using different exposures for different objects in a scene to enable objects in both bright and dark areas to be visible.

These types of scenes are typically encountered in the following scenes:

  • Entrance doors with daylight outside and a darker indoor environment
  • Vehicles entering a parking garage or tunnel, also with daylight outside and low light levels indoor
  • Vehicles with bright headlights, driving directly toward the camera
  • Environments with lots of reflected light, for example, in office buildings with many windows or in shopping malls

Figure 8. These comparisons show how detail can be lost when an image is over or under exposed due to the inability of a camera to provide WDR.



Figure 9. In this image, WDR – dynamic capture has been used, and it is clear how the image has been balanced to make all aspects in the view area visible.


Lightfinder


Axis Communications’ research and development have led to the introduction of the new and revolutionary Lightfinder technology. The Lightfinder technology is the result of a meticulous choice of the right sensor and the right lens, together with the elaboration of the image data coming from the combination of sensor and lens. The fusion of these factors – sensor, lens, in-house chip development and knowledge in image processing – provides network cameras incorporating this technology with outstanding performance.

The Lightfinder technology makes AXIS Q1602 highly sensitive to low light, allowing the camera to “see” even in dark conditions. Axis’ knowledge base about image processing, chip development, choice of sensors and day/night lenses, has enabled the innovation of cameras maintaining focus during daylight and infrared light. Axis’ knowledge heralds a new generation of surveillance cameras with outstanding performance. The fixed network camera delivers progressive scan image quality at D1 (720 x 576) resolution, in both indoor and outdoor applications, where light is poor.

The advanced Lightfinder technology will be especially beneficial in demanding video surveillance applications, such as construction sites, parking lots, perimeters and city scenes. In contrast to conventional day/night cameras that switch to black & white in darkness, AXIS Q1602 can maintain colors even in very dark conditions. There are many situations where surveillance video with color is an important factor for successful identification, and this capability greatly enhances the user’s ability to effectively identify people, vehicles and incidents. In many cases, because of the camera’s extreme light sensitivity, IR illuminators are not required, and this reduces installation costs.



Figure 10. Comparison between a standard network camera and an AXIS Q1602 camera in a low-light scene (0.3 lux).





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