About pixel densities and what they mean


An IP surveillance system may be used to observe and protect people, objects and people’s activity inside and outside the objects, traffic and vehicles, money handling in banks, or games in casino environment. All of these objects of interest may have different clarity when displayed on a workstation screen. The image clarity depends primarily on the camera used, the imaging sensor, its lens and the distance from the object.

There is one parameter in IP CCTV that expresses the image clarity in a simple way with just one parameter – Pixel Density. The Pixel Density is usually expressed in pixels per metre (Pix/m), at the object plane, although it can be expressed in pixels per foot. Pixel Density in IP CCTV sense should not be confused with the Display Pixel Density quoted by various LCD display manufacturers which defines the screen density, in Pixels Per Inch (PPI).

The advantage of expressing object clarity with its Pixel Density is that it combines the sensor size, pixel count, focal length and distance to the object in just one parameter.

This is one of the main functionalities of the ViDi Labs Calc application.

When using Pixel Density metrics all variables are included and makes it universally understandable what details you will get on an operator’s workstation screen.

When designing a system, or a tender for a system, one can request Pixel Density for a particular image quality. So, instead of asking for a 6 mm lens for your camera in a particular location, for example (which means nothing without knowing the camera sensor it is used on), it would be much more useful if a particular Pixel Density is defined for the view. This will then be used to calculate the required lens for the particular camera used and the distance from the object. This will guarantee the clarity of the image (assuming the lens is focussed optimally and there is sufficient light, of course). This can be done very easily with the ViDiLabs Calc. Pixel Density can be used for any object that IP CCTV user might be interested in: face, licence plate, playing card, money and similar…Click HERE to read full article.