In an era of heightened terror threats or fear of organised attacks, the demand for more cctv surveillance camera is becoming increasingly insistent. But is the “more is better” approach really the right one in this case? Rather than just increasing the number of ip security camera, would efforts not be better spent on making the video systems more efficient – with the right technology, that would not even be very difficult.
Whether they be public spaces, airports or business premises: the challenge when it comes to safeguarding large areas and expanses is to be able to obtain a comprehensive overview of the entire surveillance area and at the same time the highest possible resolution of details in even the most distant regions of the image.
Resolution is not everything
Manufacturers of network IP CCTV Security Camera may vaunt larger and larger megapixel numbers: but resolution alone is not everything. In order to be able to provide reliable security over large expanses, it is imperative to be able to make out details and identify individuals not only close to the camera but also in more distant regions. And this is where a very simple physical principle takes effect: a real scene is three-dimensional, but in the outdoor cctv camera image it is only represented in two dimensions. The camera pixels are distributed evenly over the camera sensor, which means that the advertised resolution is also constant for the entire image angle – even though a much higher resolution and pixel density might really be needed for more distant regions in order to deliver the same number of pixels per metre as are available for a region closer to the camera.
In other words: If a camera delivers a high-resolution overview image, this can be used to render sequences of events visible, depending on the lighting conditions at the site and the dynamics of the camera. But this certainly does not mean that the resolution over the entire scene is sufficient to allow incidents to be investigated in an emergency. In such situations, the following condition must also be met: Depending on the requirement, and as appropriate for the image scene and details that are important to recognise, a minimum number of pixels must be present on the object or person in the image. This is referred to as pixels per metre (pix/m) on the object/person. It is not the same as the number of pixels a camera uses (as described in the statement “5 megapixel camera”, for example).
Guideline values have been established in the video industry for pixels per metre: To observe, you need 62 pixel/m, to recognise known individuals you need 125 pixel/m, and 250 pixel/m are needed in order to be able to identify unknown persons – regardless of how far from the IP Cameras the people are.