Security Camera Lens Calculator
Choose a lens and a distance to see how wide the camera sees there, and whether the picture is sharp enough to watch an area, recognize a person or identify a face.
| Job | Needs | At your distance | Works up to |
|---|
Aim real cameras on your own property. The free Silarius Site Planner shows each camera’s view on a satellite map or floor plan and picks the lens for every spot.
Open the Site PlannerWide lens or long lens?
A short lens (2.8 mm) sees a wide area but makes far-away people small. A long lens (8 mm or 12 mm) sees a narrow strip but keeps detail far away. Most homes and shops use 2.8 mm or 4 mm near the building, and a longer lens for a gate, a driveway entrance or the far end of a parking lot.
What “pixels per foot” means
Detail depends on how many pixels cover each foot of the scene. Common guidelines:
| Pixels per foot | What you can do |
|---|---|
| 20 or more | Watch an area: see that someone is there and what they are doing |
| 40 or more | Recognize a person you know, read large signs |
| 80 or more | Identify a stranger’s face clearly |
Lens angles here are typical values. Silarius 2.8 mm models measure 96° to 105° depending on the model, and 180° panoramic models cover what usually takes two cameras.
Questions
Is 2.8 mm or 4 mm better?
2.8 mm covers more width and suits porches, rooms and small yards. 4 mm sees narrower but keeps the same detail about 50% farther away, which suits driveways and storefronts.
How far can a security camera see a face?
It depends on the lens and resolution. A 5MP camera with a 2.8 mm lens identifies faces out to about 13 feet; with an 8 mm lens, about 44 feet. Use the calculator above for your camera.
Does a higher resolution camera see farther?
Yes. With the same lens, a 4K camera keeps the same detail about 50% farther away than a 5MP camera, because it has more pixels across the picture.