How is pixel density defined?

Pixel density is defined as the number of pixels that cover a target area, which is typically expressed in pixels per inch (PPI) or pixels per square inch (PPI²). This measurement is significant because it indicates how detailed an image can appear—higher pixel density means that there are more pixels available to represent the details of the captured scene, resulting in sharper and clearer images.

Considering the other options, the total number of pixels in an image refers to the overall pixel count but does not provide insight into how closely they are packed within a specific area. The resolution of the display device indicates how many pixels it can show horizontally and vertically but does not inherently define pixel density. Lastly, the maximum number of colors in an image pertains to the color depth rather than the density of pixels; it speaks to how many different colors can be represented rather than how tightly those pixels are arranged.

Thus, understanding pixel density in terms of coverage over a target area is crucial for evaluating the clarity and detail of images produced in video surveillance applications and other fields.