Decide what the picture must tell you
Detecting someone means noticing a person is present. Observing means seeing more of their activity and appearance. Recognising someone means judging whether they are someone already seen or known. Identifying someone requires enough usable distinguishing detail to establish who they are. These are different design aims, not guarantees attached to a camera's megapixel label.
A wide overview and a detailed entrance view do different jobs
A camera covering an entire yard spreads its pixels across a large scene. A second view aimed at a controlled entrance can put more pixels on the person passing through it. The original diagram below illustrates coverage geometry only; it is not a measured detection-distance chart.
Higher megapixels alone do not guarantee identification quality
Recorded detail also depends on the lens, distance, angle, lighting, exposure, movement, compression and display. Digital enlargement cannot restore detail that was never captured. Manufacturer DORI distances are planning references under stated assumptions, not proof that a real face or vehicle plate will be identifiable in every condition.
Distance and lens choice
As distance increases, a person generally occupies fewer pixels. A wider lens includes more of the scene, while a narrower view can concentrate detail on a smaller area. An adjustable lens helps frame the intended target during commissioning. It cannot see through parked vehicles or round a corner. Compare selected cameras by their actual view and lens.
Mounting height and angle
Height can protect a camera and provide an overview, but a steep downward angle may hide a face. Choose a position where the likely route presents useful detail without creating an accessible tampering point. Check doors, foliage, parked vehicles and changing stock levels for obstructions.
Lighting and movement
Test the view after dark as well as in daylight. Backlighting at a doorway, headlights and infrared reflections can overwhelm useful detail. Shorter exposure can help freeze movement but needs enough light. Colour-night operation needs visible light; night-vision checks explain common problems.
Record, replay and check the intended task
Walk the agreed routes during commissioning with permission. Check the recording, not just live view, at the expected distance and lighting. Verify that the selected stream is being saved and that authorised users can export a sample. Review neighbouring property and privacy-sensitive areas when agreeing the view.
Design the complete system
The plan connects camera choice to positioning, cable routes, PoE, switching, the recorder and storage capacity. Request a CCTV Survey for a home or commercial installation.
Further Reading
Axis explanation of pixel density and scene conditions. Manufacturer instructions are model-specific; check applicability before changing settings.