Free tool
Camera field of view calculator.
Enter the camera's viewing angle, its resolution and how far away the target is. See how wide an area it covers, and whether it can identify a face there.
How camera field of view works
A camera sees a wedge that widens with distance. Its angle sets how wide it is at the target; its pixels, spread across that width, set how much detail is there.
Area width = 2 × distance × tan(angle ÷ 2)
Pixels per foot = horizontal pixels ÷ area width
1.Set the camera
Its horizontal angle and resolution, from the datasheet. The lens buttons fill in a typical angle.
2.Place the target
How far away along the floor, how high the camera is, and how high the face.
3.Read the answer
Identify, recognize, observe or detect, how far each holds, and the lens that reaches it.
How much detail each task needs
| Level | Pixels per meter | Pixels per foot |
|---|---|---|
| IdentifyA stranger, beyond doubt | 250 | 76.2 |
| RecognizeSomeone you know | 125 | 38.1 |
| ObserveWhat a person is doing | 62.5 | 19.1 |
| DetectThat a person is there | 25 | 7.6 |
Worth knowing
Use the datasheet angle
Security lenses see wider than their size suggests: a 2.8 mm usually covers 100 to 106 degrees.
Height adds distance
A camera up high is farther from a face than the floor distance, and cannot see the floor right below it.
Center or across the picture
Datasheets measure detail at the center, where there is more. Plan across the picture when the whole width matters.
Need more detail?
Move closer, use a narrower or varifocal lens, or a higher resolution. Plates need their own check.
Put a narrow camera where faces pass
A wide camera covers the scene. A door or gate needs a narrower lens to identify who comes through.
A 2.8 mm 4 MP camera at face height identifies to about 13.4 ft across the picture, 18.7 ft at the center.
Where these figures come from
The detail levels come from the international CCTV standard; the lens figures from a camera maker's datasheet.
Detail and lenses
Pixels each task needs (DORI)
Identify 250, Recognize 125, Observe 62.5, Detect 25 pixels per meter
IEC 62676-42014
A 4 MP camera's angle and Identify distance
2.8 mm: 103°, Identify 6 m; 4 mm: 84°, Identify 8 m
These are typical datasheet angles NexVolt starts on, and a working figure. Use your camera's own:
Common questions
How far can a 2.8 mm camera identify a face?
Not far. A 4 MP camera at 103 degrees, level with the face, holds the Identify level (250 pixels per meter) to about 13.4 ft averaged across the picture, or 18.7 ft at the center, which is how datasheets measure it. A 2 MP camera reaches about 10 ft and an 8 MP one about 20 ft. A wide lens is for covering a scene; identify faces with a narrower camera at the door.
What lens do I need to identify someone at 30 ft?
With a 4 MP camera mounted 10 ft up, the view must be 57.9 degrees or narrower to hold Identify at 30 ft along the floor: in the common sizes, a 6 mm lens (52 degrees). A varifocal lens lets you set the exact width on site. The calculator shows the angle for each level at whatever distance you enter.
What are the DORI levels?
They are the DORI levels from the CCTV standard IEC 62676-4, set by how many pixels cover a meter of scene: Detect 25 pixels per meter (about 7.6 per foot), enough to see a person is there; Observe 62.5 pixels per meter (19.1), enough to see what they are doing; Recognize 125 pixels per meter (38.1), enough to recognize someone you know; Identify 250 pixels per meter (76.2), enough to identify a stranger.
Does mounting a camera higher make it worse?
Yes, a little, and it leaves a blind spot. A camera 10 ft up looking at a face 30 ft away is farther from it than 30 ft, and it cannot see the floor nearer than about 13 ft when aimed at the target. At 8 ft the blind spot shrinks to about 12 ft. Mount high enough to resist tampering, then check the detail at the face, not along the floor.
Is a 4K camera worth it?
For detail at a distance, yes: on the same 103 degree lens an 8 MP (4K) camera identifies to about 20 ft against 13.4 ft for 4 MP. It also needs about twice the storage and bandwidth, and smaller pixels see less in the dark. Often a 4 MP camera with a narrower lens gives the same detail where it matters for less.
Why do datasheets give longer distances?
Datasheets measure detail at the center of the picture, where a security lens has the most pixels per foot; averaged across the whole width it is lower. Choose "At the center" above to compare with a datasheet, and plan on "Across the picture" when a face could be anywhere in the frame.
Can this camera read license plates?
Plate reading needs its own check. DORI is defined for people, and a plate usually needs more detail than Identify, a narrow view, a fast shutter and infrared light at night. Use the camera maker's plate-reading figure, and a dedicated plate camera for gates and entrances.
Does the detail hold at night?
Not fully. With infrared on, the picture turns black and white, noise rises and the camera may lower its frame rate, so a camera that identifies by day may only recognize at night. If faces matter after dark, plan one level above what you need, or add light.
