No matter how good your surveillance camera may be in terms of resolution or with superior features for overcoming challenging lighting scenarios, if the camera itself is subject to movement or vibrations, such as due to high winds or on being placed near moving vehicles, the images will blurry and the footage limited in terms of its use. That is unless your camera also has a high quality image stabilization feature that is able to reduce or even eliminate the effects of movement on the camera’s footage.
Following on from our previous articles about wide dynamic range and de-fog functions in our series focused on improved video surveillance image quality, this post will take a look at the types of image stabilization technology on the market and how this could enhance you video surveillance footage.
When and why is image stabilization necessary?
Image stabilization is incredibly important, especially for cameras mounted outside or positioned in exposed areas where the device may be subject to frequent and severe movements. For cameras exposed to such movement, the images produced can be blurry which in some cases can make them useless, for example when trying to see detail such as a person's face or a car's license plate number.
Moreover, the higher the image quality of a camera, both in terms of higher resolution and more powerful zoom, the more noticeable the blurriness of the image will become to the viewer; the shake or movement of the camera will increase proportionally to the amount of zoom used.
One straight forward solution for the issue of camera movement is ensuring the camera is fitted with a strong and stable mount. However, as cameras get smaller and lighter, they become more sensitive to surrounding movement that can ultimately affect the quality of the images captured.
It is therefore important to overcome this problem to ensure you are able to achieve higher and more reliable image quality at all times.
There are two main types of solutions for image stabilization: optical image stabilization and electronic image stabilization, as described below.
Most surveillance cameras on the market tend to employ electronic image stabilization, since it is a reliable and cost effective way to counteract vibrations or movement of the camera.
Optical image stabilization (OIS)
Optical image stabilization works through movement of components within the camera itself to counteract the movement of the whole camera from outside. The camera detects movement via motion sensors then it automatically starts to shift the position of the lens, or in some cases the camera's light sensor, to ensure that light always hits the camera's image sensor at the same place, as if there was no movement of the camera in the first place. With no variation in where light hits the image sensor (unlike if there is no optical image stabilization function on), the image captured is clear and consistent with no blurriness.
Electronic image stabilization (EIS)
In contrast to OIS, electronic image stabilization (also known as digital image stabilization) is a solution based on analyzing the images captured while the camera is moving. It can therefore be seen as a reactive rather than proactive solution to the problem. Through various algorithms, the camera is able to detect pixels outside the border of the standard field of vision (captured because of the camera's movement) and by using the information on these pixels the electronic image can be shifted from frame to frame to counterbalance the movement of the camera therefore ensuring that the video is clear and not blurry. This does mean, however, that the final image is slightly smaller than the full capability of the camera since some of border areas of the image will be discarded. This can result in slight loss of image quality, but is not severe.
EIS is more widely adopted within surveillance cameras mainly because it is a more cost effective solution as it does not involve moving parts within the camera like OIS.
However, due to the nature of EIS, cameras which employ this technology can sometimes mistake objects passing quickly through the field of vision as actual vibrations or movement of the camera. This difficulty in distinguishing between perceived motion and actual movement of the camera can result in the EIS function being activated at the wrong time, producing images wherein the background moves around a central stationary object (such as a bouncing ball). Although this problem is not particularly common, it can result in completely ineffective video footage.
The bottom line
For many surveillance cameras mounted outdoors, some form of image stabilization is necessary, especially if placed in a position vulnerable to wind, vibrations or other movement. Not only with image stabilization reduce blurriness and improve image quality, but in addition, if your camera has a good image stabilization function then you are not so limited by the mounting options, making the camera easier to install. Another advantage of using image stabilization is that it will save end users band width use and storage space because the camera's footage contains less movement and less unwanted video or image noise that will be present in blurry footage.
OIS is generally agreed to be a more effective form of image stabilization than EIS, but EIS is more widely adopted since it is cheaper and easier to produce. However, video surveillance experts Axis Communications have devised an image stabilization solution which combines aspects of both solutions: the camera contains a motion sensor the data from which can be used to alter the camera's images via EIS. To see the impressive results, check out this video below:
For more information about how or when to adopt image stabilization features or to find out more about all sorts of video surveillance solutions, feel free to contact us via firstname.lastname@example.org.
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