Security Camera Types: IP vs AHD Cameras, PoE, NVR vs DVR and Cable Selection
IP vs AHD (analogue HD) cameras, dome, bullet and PTZ types, megapixel and lens angle choice, PoE power classes, recorder disk sizing and cable distances.
Security camera systems split into two technologies: analogue HD (AHD, TVI, CVI) cameras that send video over coaxial cable to a recorder (DVR), and IP cameras that send video as data over the network (NVR). Resolution, lens angle, housing, cable distance and recording time decide the choice.
> Related Category: Browse cameras and cables in Security Cameras, Ethernet (LAN) Cables and Coaxial Cables.
1. IP vs AHD cameras
| Feature | AHD / TVI / CVI (analogue HD) | IP camera |
|---|---|---|
| Recorder | DVR | NVR |
| Cable | Coaxial (RG59) plus separate power | One Cat5e / Cat6 cable |
| Power | 12 V DC adapter or central supply | PoE over the data cable |
| Typical resolution | 2–5 MP, up to 8 MP | 2–8 MP and above |
| Cable distance | 200–300 m (depends on resolution) | 100 m (extended with switches) |
| Smart analytics | Limited, in the recorder | In the camera: person/vehicle detection, line crossing |
| Best for | Renewing an existing coaxial installation | New installations, high resolution, remote viewing |
Hybrid recorders accept both camera types and offer a practical way to add IP cameras to an analogue system.
2. Camera types by housing
| Type | Property | Use |
|---|---|---|
| Dome | Ceiling mounted; viewing direction is hard to see | Indoors, shops, offices, lobbies |
| Bullet | Cylindrical, long IR range, sunshield | Facades, car parks, gardens |
| PTZ (speed dome) | Motorized pan, tilt and optical zoom | Large areas, operator monitoring |
| Wi-Fi camera | Wireless data; still needs a power cable | Homes, small shops, points without cabling |
| Fisheye | 180–360° view | Wide indoor area with one camera |
Outdoor cameras need at least IP66, and an IK10 housing where impact is likely.
3. Resolution and lens choice
| Resolution | Pixels | Use |
|---|---|---|
| 2 MP (1080p) | 1920 × 1080 | General monitoring |
| 4 MP | 2560 × 1440 | Entrances needing faces and detail |
| 5 MP | 2592 × 1944 | Wide area plus detail |
| 8 MP (4K) | 3840 × 2160 | Car parks, number plates, large open areas |
| Focal length | Approximate horizontal angle | Use |
|---|---|---|
| 2.8 mm | 100–110° | Rooms, entrances, wide areas |
| 3.6–4 mm | 80–90° | General purpose |
| 6 mm | 50–55° | Corridors, doors, medium distance |
| 12 mm | 25–30° | Distant points, number plates |
Longer focal length narrows the angle and enlarges distant objects. A varifocal lens (e.g. 2.8–12 mm) gives adjustment freedom on site. IR range (typically 20–40 m) must cover the viewing distance at night.
4. PoE and cable selection
PoE powers an IP camera over the data cable, so no adapter is needed at each camera.
| Standard | Power per port | Use |
|---|---|---|
| IEEE 802.3af (PoE) | 15.4 W | Fixed dome and bullet cameras |
| IEEE 802.3at (PoE+) | 30 W | PTZ, heated and high-power IR cameras |
| IEEE 802.3bt (PoE++) | 60–90 W | Large PTZ and multi-sensor cameras |
- The switch's total PoE budget (e.g. 8 ports, 120 W) must exceed the sum of the cameras.
- Ethernet is limited to 100 m; use solid copper Cat6 cable for PoE. Copper-clad aluminium (CCA) increases voltage drop and heating; see CCA vs Solid Copper Cable.
- In analogue HD systems video runs on RG59 coax and power on two separate cores; combined CCTV cables simplify installation. See Coaxial Cable and F Connector Wiring.
- On long 12 V runs voltage drop can switch the camera off at night when IR turns on; use a larger conductor or supply power near the camera.
5. Recorder and disk sizing
Choose more channels than cameras (4, 8, 16, 32). Disk space follows from bit rate:
Disk (GB) = bit rate (Mbps) × 10.8 × cameras × days
(1 Mbps recorded continuously takes about 10.8 GB per day.)
Example: four 4 MP cameras with H.265 at 3 Mbps each for 30 days:
`3 × 10.8 × 4 × 30 ≈ 3,900 GB` → a 4 TB disk.
- H.265 needs roughly half the space of H.264 at the same quality.
- Motion-only recording cuts disk needs by 50–80% depending on scene activity.
- Use surveillance-class disks built for continuous writing.
Cameras in workplaces and shared areas fall under data protection law; a visible notice and privacy information are required.
Frequently asked questions
Is an IP camera or an AHD camera better?
IP is preferred for new installations: one cable for data and power, higher resolution and analytics in the camera. Where sound coaxial cabling exists, AHD allows renewal without recabling.
What is the difference between a DVR and an NVR?
A DVR digitizes and records coaxial signals from analogue HD cameras. An NVR records digital video sent by IP cameras over the network; models with PoE ports power the cameras directly.
How many megapixels are enough?
2 MP is enough for general monitoring. Choose 4–5 MP at entrances where faces matter and 8 MP for number plates and large open areas.
2.8 mm or 3.6 mm lens?
A 2.8 mm lens sees about 100–110° and suits rooms and entrances. A 3.6 mm lens narrows the view to 80–90° and slightly enlarges objects.
How many TB do 4 cameras need for one month?
About 3.9 TB with H.265 at 3 Mbps per camera recording continuously; a 4 TB disk is enough. Motion recording lowers this considerably.