CCTV lens calculator
See how wide an area a camera covers at a given distance, and how much detail you get there.
Formula: field of view = 2 × atan(sensor width ÷ (2 × focal length)); coverage = 2 × distance × tan(field of view ÷ 2). Sensor widths are for 4:3 formats from Opto Engineering and Machine Vision Direct. Levels follow IEC 62676-4:2014 (Axis white paper). Real cameras differ because of lens distortion and the part of the sensor they use, so the datasheet value is more accurate when you have it.
How to read the result
- Shorter focal length, wider view. A 2.8 mm lens covers a wide area but with less detail at a distance; a longer lens shows less area with more detail.
- Pixel density decides detail. The same camera that identifies a person at the door may only detect someone at the far end of the yard.
- Pick the lens for the job. Covering a whole parking lot and reading faces at an entrance usually need different cameras.
Detail levels (DORI)
| Pixel density | What it means | |
|---|---|---|
| Detect | 25 px/m | You can tell whether a person or vehicle is there |
| Observe | 63 px/m | You can see what a person is doing and some details such as clothing |
| Recognize | 125 px/m | You can tell whether it is someone you have seen before |
| Identify | 250 px/m | You can identify the person beyond reasonable doubt |
From IEC 62676-4:2014 as summarized in Axis’s white paper “Pixel density based on IEC 62676-4:2014”, checked November 2026. A second edition was published in 2025.
After choosing your cameras
Litmus NVR records your cameras for free on Windows, Mac or Linux and turns every person and vehicle it detects into a card, so you can find who was there without scrubbing through hours of video.
Questions
Why is my camera’s datasheet field of view different from the result?
Many cameras use only part of the sensor for a 16:9 picture, and wide lenses have distortion. When the datasheet lists the horizontal field of view, enter it in the calculator to use that value.
What resolution do I need to identify a face?
IEC 62676-4 sets 250 pixels per metre at the person’s distance for identification. Enter your resolution and distance to check whether a camera reaches it.
Is Litmus NVR really free?
Yes. Every feature is free with no camera limit. Live View over a direct connection is unlimited.
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