A Hikvision thermal camera looks at heat differences, not normal scene colour. That is why it is used for perimeter detection, fire-risk monitoring, and difficult environments rather than everyday front-door or cashier coverage.

Bi-spectrum cameras are often the most practical thermal cameras for real security jobs because they combine a thermal channel and a visible optical channel in the same unit. That gives the site both earlier detection and ordinary scene context.

Thermal resolution affects how much useful heat detail the camera can gather from the scene. It does not automatically tell you exact distance performance on its own, but it does strongly affect how well the camera scales from a small close scene to a larger and harder one.