The short answer: 4 MP for the vast majority of installations, 8 MP only for large scenes. The long answer explains why, and why a criterion no one talks about matters more than resolution.
What Resolution Actually Measures
A 4 MP camera produces an image of approximately 2560 × 1440 pixels. An 8 MP camera goes up to 3840 × 2160, which is 4K. The number of pixels doubles, but the linear definition—the one that determines if you can recognize a face—only increases by about 50%.
This is the first misunderstanding: going from 4 to 8 MP does not double your identification capacity. You gain half a step, for bandwidth and storage that, in contrast, genuinely double.
The Criterion That Really Matters: Pixels Per Meter
Professionals don't think in megapixels but in pixels per meter (px/m) for the area to be monitored. The accepted orders of magnitude:
| Objective | Required Density | What You Get |
|---|---|---|
| Detection | ~25 px/m | Someone is there |
| Observation | ~62 px/m | Silhouette, clothing, behavior |
| Recognition | ~125 px/m | It is indeed the person I know |
| Identification | ~250 px/m | Usable for a complaint |
The consequence is counter-intuitive: a 4 MP camera tightly framed on a door identifies better than an 8 MP camera sweeping an entire parking lot. Resolution is distributed across the width of the scene. Doubling the scene halves the density.
Frame before increasing resolution. This is the most cost-effective advice in this article.
When 4 MP is the Right Choice
Entrance door, hallway, lobby, cashier, driveway, gate, patio, garage: anywhere the scene is less than six or seven meters wide, 4 MP provides the exact same identification result as 8 MP, while occupying half the disk space.
It also has a less visible advantage: for the same sensor size, fewer pixels mean larger photosites, hence better low-light sensitivity. Many 4 MP cameras produce a cleaner night image than their 8 MP equivalent.
When 8 MP is Justified
Parking lot, full facade, loading dock, company yard, warehouse, open field: as soon as the scene exceeds about ten meters in width.
The real benefit is not the beauty of the live image—on a screen, the difference is barely visible. It's the ability to reframe in the recording after the fact: you zoom in on a license plate, a face, a detail you didn't know you needed to monitor at the time of installation. In a wide scene, this is what makes the difference between an image and evidence.
Impact on Storage
Orders of magnitude for 30 days of archiving with motion-triggered recording:
| Cameras | 4 MP | 8 MP / 4K |
|---|---|---|
| 2 | 2 to 4 TB | 4 to 8 TB |
| 4 | 4 to 8 TB | 8 to 16 TB |
| 8 | 8 to 16 TB | 16 to 32 TB |
For continuous recording instead of motion-triggered, double these values. Conversely, WizSense cameras, which only record human or vehicle presence, significantly reduce volume: they ignore foliage, rain, and light changes.
The Most Frequent Sizing Error
Eight 8 MP cameras can exceed the maximum input bandwidth of an entry-level 8-channel NVR, even if all eight ports physically exist. Symptoms: dropped streams, incomplete recordings, an overheating recorder.
Always check the total supported bandwidth in Mbps on the recorder's specification sheet, not just its number of channels. With 4 MP, this issue generally does not arise.
Our Recommendation
Don't use the same resolution everywhere. The most effective configuration for a home or business combines:
- 4 MP for access points—door, gate, garage, cashier
- 8 MP for the overview—garden, parking lot, facade
You get identification where it matters and reframing where it's useful, without exploding storage costs.
Frequently Asked Questions
What about 2 MP?
Still valid for a small room or a hallway where subjects pass within three meters. Beyond that, it quickly shows its limitations.
Is 5 MP a good compromise?
Yes, for intermediate areas. Be careful with the format: some 5 MP sensors are 4:3 and not 16:9—taller field, less wide. Perfect for a hallway, less so for a facade.
Do I need Full-Color?
For a main access point, yes. Being able to describe the color of clothing or a vehicle often changes the outcome of an investigation, whereas infrared only provides black and and white.
Can I mix resolutions on the same NVR?
Yes, and it's recommended. The NVR manages streams independently.
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