Security Camera Lens Field of View Chart
On the default 1/2.8 inch residential sensor, a 2.8 mm lens covers an 84.9 degree horizontal field of view, wide enough to span 18.3 metres of scene at 10 metres distance; a 12 mm lens narrows that to 24.1 degrees and 4.3 metres. Field of view depends on both focal length and sensor width, not focal length alone.
A lens's field of view comes from two numbers together: focal length and sensor width. The standard formula is horizontal field of view = 2 x atan(sensor width / (2 x focal length)). A "4 mm lens" spec sheet entry is meaningless for field of view until paired with the sensor it sits in front of.
The tables below use the industry default residential sensor width, 1/2.8 inch (5.12 mm), unless a table specifically compares formats. Scene width at a distance follows from the field of view: scene width = 2 x distance x tan(field of view / 2), the number that turns a lens spec into a picture of what the camera actually frames.
| Focal length | Horizontal FOV | Vertical FOV | Scene width at 10 m | Scene width at 20 m |
|---|---|---|---|---|
| 2.8 mm | 84.9° | 54.4° | 18.3 m | 36.6 m |
| 3.6 mm | 70.8° | 43.6° | 14.2 m | 28.4 m |
| 4 mm | 65.2° | 39.6° | 12.8 m | 25.6 m |
| 6 mm | 46.2° | 27.0° | 8.5 m | 17.1 m |
| 8 mm | 35.5° | 20.4° | 6.4 m | 12.8 m |
| 12 mm | 24.1° | 13.7° | 4.3 m | 8.5 m |
| 16 mm | 18.2° | 10.3° | 3.2 m | 6.4 m |
| Sensor format | Nominal width (mm) | HFOV at 2.8 mm | HFOV at 6 mm |
|---|---|---|---|
| 1/4 | 3.6 mm | 65.5° | 33.4° |
| 1/3 | 4.8 mm | 81.2° | 43.6° |
| 1/2.9 | 4.96 mm | 83.1° | 44.9° |
| 1/2.8 | 5.12 mm | 84.9° | 46.2° |
| 1/2.7 | 5.37 mm | 87.6° | 48.2° |
| 1/2.5 | 5.76 mm | 91.6° | 51.3° |
| 1/2 | 6.4 mm | 97.6° | 56.1° |
| 1/1.8 | 7.18 mm | 104.1° | 61.8° |
| Focal length | Scene width at 5 m | Scene width at 10 m | Scene width at 20 m | Scene width at 30 m |
|---|---|---|---|---|
| 2.8 mm | 9.1 m | 18.3 m | 36.6 m | 54.9 m |
| 4 mm | 6.4 m | 12.8 m | 25.6 m | 38.4 m |
| 6 mm | 4.3 m | 8.5 m | 17.1 m | 25.6 m |
| 8 mm | 3.2 m | 6.4 m | 12.8 m | 19.2 m |
| 12 mm | 2.1 m | 4.3 m | 8.5 m | 12.8 m |
Why does the same lens spec list different fields of view across brands?
Because "the same lens spec" usually is not the same, once the sensor is accounted for. Manufacturers use different sensor formats even at an identical resolution, and a spec sheet often lists focal length prominently while burying or omitting the sensor size. Two 4 mm lens cameras on a 1/3 inch sensor and a 1/2 inch sensor will have noticeably different horizontal fields of view, 61.9° versus 77.3° at 4 mm.
How do I pick a focal length for a specific spot?
Start from the job, not the lens number. A driveway or front door usually wants a moderate 4 to 6 mm lens for a balance of coverage and detail. A long side yard or a gate at distance benefits from 8 to 12 mm to keep enough pixels per metre for a useful DORI distance. A wide 2.8 mm lens suits an overview of an entire small yard or garage interior, at the cost of DORI distance for any one point in that frame.
The gear that matches this answer
REOLINK TrackMix PoE Dual-Lens PTZ Security Camera, 6X Hybrid Zoom
$199.99Two lenses at once, one wide for context and one telephoto for detail, which resolves the usual argument between covering the whole drive and identifying anyone on it.
- Resolution
- 8 MP
Prices change often.
Amcrest UltraHD 4K 8MP Outdoor Bullet Security IP PoE Camera, 98ft NightVision
$94.95Amcrest publishes its IR range and its lens focal length in the listing, which is rarer than it should be and is what makes a coverage calculation possible before you buy.
- Resolution
- 8 MP
- Stated IR range
- 98 ft
- Lens
- 2.8 mm
Prices change often.
REOLINK RLC-823S1 4K PoE PTZ Camera, 5X Optical Zoom
$246.49Five times optical zoom multiplies pixels per metre at the far end of a drive by five, which no amount of sensor resolution on a fixed wide lens will do.
- Resolution
- 8 MP
- Optical zoom
- 5 x
Prices change often.
REOLINK E1 Outdoor SE PoE 4K Camera with Pan and Tilt
$119.99Pan and tilt on a small PoE body, useful where one camera has to cover two directions that are not adjacent.
- Resolution
- 8 MP
Prices change often.
Common questions
What is the default sensor size used on these charts?
1/2.8 inch, with a nominal horizontal width of 5.12 mm. This is the most common sensor format on residential and prosumer security cameras as of this writing, which is why it is used as the default across this site's lens and DORI figures. Cameras built on a different format, such as 1/3 inch or 1/1.8 inch, will produce a different field of view at the same stated focal length, shown in the sensor format comparison table above.
Is a wider field of view always better for a security camera?
Not for every location. A wider field of view covers more ground per camera, which is useful for an open yard or driveway overview, but it spreads the same pixel count across more scene width, which lowers pixels per metre and shortens the distance at which the camera can still identify a face under the DORI standard. A narrow spot, like a front door or gate, generally benefits more from a moderate to narrow lens than from maximum width.
What is the difference between a fixed lens and a varifocal lens?
A fixed lens has one focal length set at manufacture and cannot be adjusted. A varifocal lens can be manually or motor-adjusted across a stated range, for example 2.8 to 12 mm, letting the same physical camera be aimed for either a wide overview or a narrower, longer-distance view after mounting. Varifocal cameras cost more but avoid guessing the exact focal length needed before installation.
How does field of view relate to a camera's advertised viewing angle?
Manufacturers sometimes advertise a single "viewing angle" figure that is the horizontal field of view, sometimes the diagonal field of view, and do not always specify which. Diagonal field of view is always larger than horizontal for the same lens and sensor, so a camera advertised at a wide-sounding diagonal angle may have a noticeably narrower horizontal field of view in practice. When comparing cameras, check which axis is being quoted.
Does field of view change between daytime colour mode and night infrared mode?
No, the optical field of view is fixed by the lens and sensor geometry and does not change when a camera switches to infrared or black-and-white night mode. What can appear to change is effective usable range, since infrared illumination has its own limited published range, and objects near the edge of the frame may be dimmer or less detailed at night even though the angle captured is identical.
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Keep going
Before you point a camera at anything. Aim cameras at your own property and your own boundary, never into a neighbour's windows or across their garden. Cameras in bedrooms, bathrooms, or anywhere else a person reasonably expects privacy are a serious legal problem, and that includes guests, lodgers and anyone who works in your home. Audio is legally different from video, many US states require the consent of every party to a recorded conversation, and several recorders capture audio by default, so check your own state before you enable it. Some places require visible notice that recording is taking place, and landlords and homeowner associations often impose their own rules on top. This is researched general information and not legal advice, and the law varies by state and by country.
And once it is installed. Change every default password, keep the firmware updated, and be clear with yourself about where the footage goes: a cloud camera means a third party holds recordings of your home, while a local recorder keeps them in your house. That is a genuine buying consideration, not a technicality.