Resolution – Pixel Count
Now, with IP, manufacturers do not even attempt to measure performance. Instead, resolution has been redefined as counting the number of physical pixels that an image sensor has.
For example, a 1080p resolution camera is commonly described as having 2MP (million pixel) resolution because the sensor used has ~2 million pixels on it (technically usually 2,073,600 pixels as that is the product of 1920 horizontal x 1080 vertical pixels). The image of an imager below shows this example:
Pixels Determine Potential, Not Quality
Pixels are a necessary, but not sufficient, factor for capturing details. Without a minimum number of pixels for a given area / target, it is impossible. See our tutorial on why Pixels Determine Potential, Not Quality.
The presumption is that more pixels, much like higher line counts, delivers higher ‘quality’. However, this is far from certain.
Just like with classic resolution measurements that used only ideal lighting conditions, measuring pixels alone ignores the impact of common real world surveillance lighting challenges. Often, but not always, having many more pixels can result in poorer resolving power in low light conditions.
Plus, cameras with lower pixel counts but superior image processing can deliver higher quality images in bright sunlight / WDR scenes.
Nonetheless, pixels have become a cornerstone of specifying IP video surveillance. Despite its limitations, you should:
Recognize that when a surveillance professional is talking about resolution, they are almost certainly referring to pixel count, not resolving power
Understand the different resolution options available
Common Surveillance Resolutions
The table below summarizes the most common resolutions used in production video surveillance deployments today. Note that VGA is no longer common except in thermal cameras, but is included here for reference of what 'standard definition' refers to.