The useful answer is rarely “buy the biggest number.” This guide turns the specification sheet into an installation decision you can defend after dark, after handover and when footage is actually needed.
Define the evidence you need
A useful camera specification begins with the view you need to prove, not the model you want to buy. Write down the target area, the distance to the subject and whether you need detection, recognition or identification. That single exercise prevents the most common mistake: installing a wide camera and discovering that faces occupy too few pixels to be useful.
Match lens, light and placement
Lens choice and placement usually matter more than headline resolution. A fixed 2.8 mm lens gives broad context, while a narrower lens puts more pixels on a gate, till or doorway. Check the night scene separately; infrared reflection, vehicle headlights and nearby walls can undo an otherwise excellent daytime view.
Check recorder and network compatibility
Finally, verify that the camera, recorder and network agree on codec, resolution, frame rate and smart-event support. ONVIF helps basic compatibility, but vendor-specific analytics may still require matching equipment. Price the storage, PoE budget, weather protection and mounting hardware before you compare bundles.
Commission the system against a written evidence goal. Save reference images and settings so future maintenance can spot gradual changes.
Can another person prove the system still works?
Record the final view, night image, bitrate, alerts, firmware and access method. A system is not finished until the owner can verify recording and export without the installer standing beside it.
Every site is different. Confirm manufacturer instructions, electrical requirements, privacy obligations and local regulations before installation.
Frequently asked questions
How many megapixels does a CCTV camera need?
Resolution only helps when the lens and placement put enough pixels on the subject. For many home views, a correctly aimed 4MP camera can outperform a badly placed 8MP camera.
Is a 2.8 mm CCTV lens always best?
No. A 2.8 mm lens gives a broad view, while a narrower field of view usually captures more useful detail at a gate, till or distant entrance.