Getting the most out of surveillance cameras in poor lighting
The digital revolution has taken over many technological spheres, and after holding out with analog for some time, video security has now followed suit. Digital signal processing (DSP) is the driving force behind the migration toward video systems in which all components use digital electronic technologies.
This movement makes it possible to achieve optimal daylight surveillance, and as DSP cameras become less expensive than their analog counterparts, users can take advantage of the additional features that these cameras offer without paying exorbitant costs. Digital, color cameras now account for 70 to 80 percent of all video camera sales as more users turn to the new features offered by DSP to meet their comprehensive surveillance needs.
Before a home or business owner decides to overhaul a current security system, he or she may be wondering how DSP works and how the technology can benefit them. By reading the information below, users can delve into the world of DSP and learn how these systems work to generate a clear picture even in dim or strikingly bright daylight.
According to Audio Precision, the signal-to-noise ratio (SNR) measures how much noise is in the output of a device relative to the signal level. The ratio is the combination of two level measurements: the output level of the device with and without an input signal. These two measurements are added together and divided to generate a SNR that is computed in decibels (dB). For video equipment, a higher SNR is preferable.
DSP cameras have better SNRs than analog cameras, which gives manufacturers the ability to use automatic gain control to increase amplification, which leads to a higher quality image even under poor lighting conditions. According to Herman Kruegle, author of, “CCTV Surveillance: Video Practices and Technologies,” cameras with DSP usually have a SNR between 50 and 54 dB. Non-DSP analog cameras, however, have an average SNR between 46 and 48 dB.
In digital video security, the camera uses digital processing or enhancement to improve the video signal; in this case, the signal itself is not digital. According to Kruegle, most surveillance cameras still use output signals instead of analog signals because the operating distance needed to transmit a digital signal wavelength is not long enough to meet the system’s needs. Output signals have a larger range, which has led security experts and manufacturers to use network cameras and equipment that can transmit signals over the internet rather than digital signals themselves.
Local area networks, wireless networks, wide area networks and intranets are all compatible with output signals and allow the system to have long distance monitoring capabilities. By combining digital processing with standard output signals, these cameras offer enhanced image features including improved quality, back light compensation, shuttering, iris control and electronic zoom and sensitivity control that allow DSP cameras to work through lighting variations within a single image.
DSP with circuitry
One popular trend within DSP technology is the use of circuitry to expand an image sensor’s range, which more closely mirrors the performance capabilities of a human eye. This technology can have a range that is 64 times larger than conventional charge-coupled device (CCD) cameras. According to Jaycar Electronics, the lens of CCD cameras focus a small portion of the scene onto an imager chip that scans the image and generates a standard video signal that can feed into the monitor or recording device. However, DSP cameras use a different technique to generate a picture.
Kruegle explained that the DSP cameras’ technique simultaneously uses a short exposure in bright portions of the image and a long exposure in the dark portions. Rather than view the picture as one concise image, DSP cameras view dark and bright light levels at the same time. Through digital processing, the bright and dim images are then developed independently of one another. After these images are created, digital signal processing combines the signals into a single, composite image that uses the clearest portions of each exposure. This enhanced image is then sent to the recorder or monitor as a single, enhanced image that is unaffected by poor lighting conditions.
The improved signal-to-noise ratios, output signals and circuitry capabilities make digital signal processing cameras a great choice to meet daytime surveillance needs, and can give a user a sense of comfort in knowing that the images generated will be crystal clear.