How to compare CCTV quotes: the two calculations that decide
Three CCTV quotes, three different systems. Two simple calculations, pixels per metre at the critical point and days of recording, show which one delivers what it promises and what has to be written down.
An accounting office in Mococa, Brazil, received three quotes for security cameras, with very different prices. The cheapest said "4-camera Full HD kit installed". The middle one promised "4 IP cameras, 30 days of recording". The most expensive had a whole page of items. The owner nearly signed the middle one. Two calculations were enough to see that it did not deliver what it promised.
A CCTV quote is like a menu without photos: "4 cameras installed" can mean anything. To compare, you need to understand three things and insist that they are written down.
Analog or IP, in a few lines
In analog HD, the camera sends its signal over coaxial cable, and the recorder (DVR) does the compressing and recording; the 12 V power runs on a second pair of wires. In IP, the camera itself delivers finished video over a network cable and, with PoE (Power over Ethernet), power travels on the same cable, with a limit of 100 m per run. Analog makes use of good coaxial cable that is already in place; IP is the natural path in new construction and when you need more resolution. Both can be right. What is not acceptable is a quote that does not say which one it is.
The calculation that shows whether a camera identifies anyone
Megapixels alone tell you nothing. What matters is how many pixels land on each metre of the scene at the critical point: the door, the gate, the till. That measure is pixel density, in px/m:
- Scene width = 2 × distance × tan(angle ÷ 2)
- Density = image width in pixels ÷ scene width
The scale that datasheets use: 25 px/m detects, 62.5 observes, 125 recognizes someone you already know and 250 identifies a stranger. If the image may become evidence, aim for 500 px/m or more at the critical point.
At the office, the middle quote used 4 MP cameras with a 2.8 mm lens (about 100°) at the door, 6 m away. The scene is 14.3 m wide: 2560 ÷ 14.3 = 179 px/m. It does not identify who comes in. The most expensive quote put a 6 mm lens at the same spot and reached 437 px/m. Lens and distance weigh as much as resolution.
The calculation for days of recording
Bitrate is the flow that fills the disk, and the conversion is simple: GB per day = Mbps × 10.8. Four 4 MP cameras in H.265, at about 2 Mbps each, add up to 8 Mbps, or 86.4 GB per day. The 1 TB disk in the middle quote fills up in 11.6 days (1,000 ÷ 86.4) with continuous recording. After that, the recorder overwrites the oldest footage. Reaching 30 days would only be possible by recording on motion, and that was not written. A recording period promised without a configuration is worthless.
What has to be written
Put every quote into the same table and check:
- Cameras: quantity, technology, resolution and the lens of each one.
- Coverage: where each camera goes and its objective, ideally with a sketch.
- Recording: recorder, surveillance disk in TB, and the number of days with the configuration that produces it (resolution, fps, compression, continuous or motion).
- Infrastructure: cable (coaxial or copper UTP), conduit, UPS and earthing.
- Remote access: default password changed at installation, one user per person and no open port on the router.
- Equipment and service warranty, execution deadline and quote validity.
- In a business: a monitored-area sign and a retention period for the images, because the image of an identifiable person is personal data under the LGPD (Brazil's data protection law).
A price far below the others almost always means a missing item. A higher price means you should see what justifies it.
How far to go on your own
Anyone can compare quotes and redo the math with a phone calculator and a tape measure. Installing is another story: the electrical part (outlet, circuit, earthing) follows NBR 5410 (Brazil's standard for low-voltage electrical installations) and must be done by a qualified professional, and a badly run cable or an exposed splice brings down the best design. The technical basis here is Brazilian; outside Brazil, follow your local electrical code and data protection law.
To keep going
This article summarizes the last lesson of the course CCTV today: analog × IP, resolution, PoE and coverage design. The checklist "Comparing 3 CCTV quotes" gives you the 8 items to check on the quotes you received, and arrives as a PDF in your inbox.
Cheap is what delivers what is written.
Marcelo Nogueira Souza — E-Nogueira, since 2014