Enhanced IP Cameras Provide Nighttime Viewing
Nighttime is when we expect criminal activity, and of course, that’s the most challenging time for IP surveillance cameras. There are several ways of seeing in the dark, but the best way is to use an IP camera with enhanced low-light sensitivity.
The low-light capability of IP cameras has gotten much better over the last few years. We used to be happy with cameras that could see at 0.1 lux in color, but now we have IP cameras (like the PNO-A6081R) that have low-light sensitivity in color at 0.007 Lux. The camera can see at night when the stars are shining.
This article reviews the technology behind very low-light IP cameras.
Review of Light Illumination Measurements
Lux is the unit of light measurement that defines the intensity of light as perceived by the human eye.
Here are some examples of the illuminance provided by various light sources:
|Illuminance (lux)||Surfaces illuminated by|
|0.0001||Moonless, overcast night sky (starlight). Requires a camera with an IR illuminator|
|0.001||Starlight (clear sky) The very low-light sensitive cameras, such as the PNO-A6081R provide a black-white image at this light level.|
|0.002||Moonless clear night sky with airglow|
|0.05–0.3||Full moon on a clear night The PNO-A6081R provides a color image at this light level.|
|3.4||Dark limit of civil twilight under a clear sky Most good IP cameras provide color video at this|
light level and brighter
|20–50||Public areas with dark surroundings|
|50||Family living room lights|
|80||Office building hallway/toilet lighting|
|100||Very dark overcast day|
|150||Train station platforms|
|400||Sunrise or sunset on a clear day.|
|1000||Overcast day; typical TV studio lighting|
|10,000–25,000||Full daylight (not direct sun)|
Technologies Required to Achieve Very Low-Light Capability in IP Cameras
Color video makes it easier to identify objects and people in the scene, but when there’s not enough light, the cameras switch to gray-scale or black/white mode. As it gets darker, the special low-light cameras stay in color much longer than standard IP cameras. Also, when there is not enough light, the video becomes noisy, and it’s hard to see the detail. The high-performance low-light cameras include better noise reduction.
Low-light type cameras require an excellent lens, a high-sensitivity sensor, and an advanced image processor to provide clear video in low-light situations.
Light Transmission of the Lens is a Key Factor for Light Sensitivity
The clearer the lens; the more light reaches the sensor
The IP Camera Lens is a critical factor in low light operation. The f-number specification defines the amount of light that can pass through the lens. The lower the f-number, the more light the lens can pass. When selecting a variable lens, the highest light transmission light (the lowest f-number) is when the lens is set to its widest angle. As the lens is zoomed (magnified), less light passes through the lens. This means that the best low-light performance is when the lens is set to the widest angle.
Here are examples of two different IP cameras.
The QNV-6082R1 is an example of an economical bullet IP camera. It can be used when there is sufficient light for the camera. The camera’s specification for low-light sensitivity is 0.03lux (Color) and includes an IR illuminator for viewing in total darkness. The lens aperture of F1.6(Wide)~F2.9(Tele)
The PNO-A6081R is an example of a very low-light camera. The light sensitivity is 0.007 Lux@F1.3, 1/30sec. (Color), and the lens has a Maximum Aperture Ratio of F1.3 (Wide) ~ F2.15(Tele). When the light is extremely low, the camera switches to night mode, and the light sensitivity is 0.0007 Lux in BW mode (F1.3, 1/30sec). When it gets darker, the IR illuminator turns on. It can be used outdoors even when the light is from the stars.
Sensor Size Matters in Low-Light Situations
The larger the sensor, the more light is captured
The sensor contains many photodiodes that convert the light into an electric signal. The amount of light that reaches the diode depends on the size of the surface exposed to the light. The larger the sensor size, the more light falls on each photodiode. Other techniques, including tiny lenses that help focus the light, can improve the light sensitivity, but the size primarily provides the most effective way to increase light sensitivity.
To learn more, read the article about How the CMOS Video Sensor Works in IP Cameras.
The Image Processor Makes a Significant Difference in Low Light
High complexity image processing technology is required to reduce noise and enhance the image.
The ability to reduce noise in an image is complex and requires much computational power. The new IP camera image processors have high-performance processors that use Spacial-Temporal computation and other algorithms to reduce noise.
As an example, the latest Hanwha Techwin cameras have advanced image processors that enhance low-light images. The cameras include high-performance noise reduction technology and an image correction technology that maintains brightness, color reproducibility, and sharpness in extremely low light environments.
Summary of How Low-Light Cameras Work
Low-light IP cameras improve the video at night exactly when it is required. As it gets darker, these cameras continue to provide color video. The cameras include very clear lenses, large sensors, and powerful image processing computers. The lens has to be very clear so it can pass as much light as possible. The photodiodes in the semiconductor sensor need to capture as much light as possible. The processor reduces the noise caused by low-light video signals. Everything works together to achieve a good image at low-light levels.
If you would like to learn more about low-light cameras, please get in touch with us at 800-431-1658 in the USA or 914-944-3425 everywhere else, or use our contact form.