Camera Coverage Distance Calculator

Camera Coverage Distance Calculator

Camera Coverage Distance Calculator

Given resolution, focal length, and scene width: max usable distance and pixel density.

Inputs

Results

Distance for that scene width-
Horizontal FoV-
Pixel density at scene-
Usable task at scene-
Effective IR night range-
Adjust inputs to see scene-coverage analysis.

How this works

  • Given focal length and sensor width, the horizontal field-of-view is fixed: FoV = 2 × arctan((sensor_width / 2) / focal). This is independent of distance.
  • Distance to a scene of given width follows from the same triangle: distance = (scene_width / 2) / tan(FoV / 2).
  • Pixel density at the scene = horizontal resolution ÷ scene width (in feet). Compare to IEC 62676-4 thresholds (8 / 19 / 38 / 76 px/ft) to determine the usable task.
  • Night-vision range is the minimum of the optical reach and the IR illuminator's effective range — pixel density at IR-limited distance is what matters at night.
IR ranges quoted by manufacturers assume a near-100% reflective subject (white shirt). Real-world dark-clothing reach is ~60% of spec. Plan IR for the longest realistic event distance, not the catalog headline number.

Worked example

4MP camera with a 1/2" sensor, 6mm fixed lens, looking at a 30 ft wide loading dock entrance:

  • FoV = 2 × arctan((6.4 / 2) / 6.0) = ~56°
  • Distance = (30 / 2) / tan(28°) = ~28 ft
  • Pixel density at 30 ft scene = 2560 / 30 = ~85 px/ft — well above the 38 px/ft Recognize threshold
  • With high-power 100ft IR: usable distance limited by optical, not IR — night-time recognition stays solid

This camera meets Recognize-grade for any person crossing the dock threshold and Identify for those within ~14 ft of the camera. Plenty of margin for the use case.

Recommended IPSD products

Bullet Cameras with IR
Outdoor 4MP-8MP fixed and varifocal, IR ranges 100-400 ft
PTZ Cameras
Long-range identification at 200+ ft with optical zoom
Dome Cameras
Indoor and outdoor domes with built-in IR up to 100 ft
External IR Illuminators
For runs beyond camera-integrated IR (400 ft+ scenes)

FAQ

Why is real IR range less than the spec sheet?

Spec ranges are measured against a 100%-reflective target in zero ambient light. A person in dark clothing reflects ~30-40% of IR. A wet asphalt surface reflects even less. Plan for IR usable distance to be 50-65% of spec.

How does fog or rain affect this?

Both scatter IR light, reducing effective range by 50-75% in heavy weather. Cameras with smart IR (variable LED zones, anti-scatter optics) handle this better. For coastal or industrial sites, oversize IR by 2x.

What is the difference between optical and digital zoom?

Optical zoom (PTZ, varifocal) physically moves lens elements — resolution at the target is preserved. Digital zoom crops the sensor — effective resolution drops linearly with zoom factor. Always pick optical zoom for long-distance work.

Can I use this calculator for thermal cameras?

Thermal pixel counts are typically much lower (640×480 is common) and the task thresholds differ (DRI for thermal = Detection / Recognition / Identification at ~2 / 8 / 16 pixels on target). The geometry math still works; substitute the thermal-specific pixel-on-target requirement.

What focal length should I default to?

For general-purpose work, a 2.7-13.5mm motorized varifocal covers ~85° to ~30° FoV — suitable for everything from corridors to mid-range parking lots. Commission tight on day one, then loosen if needed. Fixed-lens cameras lock you to one configuration.

Related guides

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