Field of View and DORI

How to use

1. Enter the lens focal length and the aspect ratio. The calculator assumes a 5.37 mm sensor, typical of a 1/2.8 in surveillance camera. That assumption is stated under the lens. Change it only if you know the format or the published millimetre width.
2. If the datasheet lists a horizontal field of view angle, switch to Datasheet angle. That path uses no sensor assumption and the result is exact.
3. Set horizontal resolution and the distance to the target. Read the scene width, the pixel density, and the four IEC 62676-4 distances. The lens table lists common focal lengths on the same assumed or entered sensor. None of those rows is marked as the answer.
4. 1:1 is a fisheye path: published field of view, mounting height, and a usable half-angle. 21:9 is a panoramic path: total horizontal resolution and the published total horizontal angle.

Assumptions

• DORI figures assume the target is in the centre of the frame, adequately lit, and not moving faster than the shutter can handle.
• Lens distortion at wide angles reduces usable density at the edges of the frame.
• The default sensor width is 5.37 mm, typical of a 1/2.8 in 16:9 part. Nominal sensor formats are marketing labels, not measurements. The datasheet field of view angle is the exact figure.
• Published angles for wide lenses often run wider than the rectilinear calculation from sensor width and focal length, because short lenses distort.
• IEC 62676-4 thresholds are Detect 25 px/m, Observe 63 px/m, Recognise 125 px/m, and Identify 250 px/m (7.6, 19.2, 38.1, and 76.2 px/ft).
• A 1:1 fisheye is treated as equidistant (radius proportional to angle). Some fisheyes are closer to equisolid. The manufacturer’s coverage chart governs. DORI distances do not translate directly. Dewarping redistributes pixels rather than adding them.
• A 21:9 panoramic is usually several sensors in one housing. Density uses the total horizontal resolution and the published total horizontal angle. The per-sensor angle is what governs distortion at the seams.
• Licence-plate capture is not a DORI level. Plates need far more density than a face and depend on lighting, angle, and shutter speed.
• Plate legibility also depends on plate condition, lighting, vehicle speed, shutter speed, and approach angle. The distance reported in the licence-plates appendix is the pixel-density ceiling, not a guarantee of a read.
• Mounting coverage assumes flat, level ground and a camera perpendicular to the wall.
• The camera datasheet governs. The result is an estimate to verify against manufacturer data, the AHJ, and current applicable code.

FAQ

Why does the page assume a sensor width?

Focal length alone cannot produce a field of view. The same lens is narrow on a small sensor and wide on a large one. The default is 5.37 mm, typical of a 1/2.8 in surveillance camera. That is an assumption, not a measurement. The datasheet angle needs no such guess.

What to do when the datasheet only gives the angle?

Use Datasheet angle and enter the horizontal field of view plus the horizontal resolution. That path does not assume a sensor width. The result is exact.

Why is a published 2.8 mm angle often 100° instead of 87°?

The rectilinear formula maps the sensor through a tangent. Short lenses distort, so the published angle often runs wider than that calculation. When both figures are on the sheet, the datasheet angle is the one to trust.

What does 1:1 (fisheye) report?

A fisheye is not rectilinear. This page assumes an equidistant projection and reports pixel density directly below the camera, the ground radius where each DORI threshold is crossed, and a usable half-angle as the practical outer edge. It does not print a 180° coverage diameter. Some fisheyes are closer to equisolid, so the manufacturer’s coverage chart governs.

What does 21:9 (panoramic) use?

The total horizontal resolution across all sensors and the published total horizontal angle. A multi-sensor panoramic is several cameras in one housing. The per-sensor angle is what governs distortion at the seams.

Why are licence plates their own problem?

Identify is a face-level density. A plate is smaller, often at an angle, and needs a shutter fast enough to freeze a moving vehicle. Lighting on the plate is a separate constraint. Those sit outside the IEC 62676-4 levels.

What separates a dedicated LPR camera from a camera that happens to see plates?

A dedicated LPR camera is installed to the manufacturer’s published envelope: height and offset ranges, angle limits, capture distance, shutter speed, IR matched to plate retroreflectivity, and how many lanes it is rated to cover. That is not a DORI question. A general-purpose camera that should produce a readable plate in playback is a pixel-density question. The appendix reports that density and the distance at which the current camera meets it.

Why do plate reads fail at angles and heights that look fine for general video?

A plate that is still visible can already be unreadable. Off-axis angle, height outside the published range, and IR glare on a retroreflective plate all stop a read before they stop a general scene. Shutter speed that is slow enough for a pretty overview image also smears characters on a moving vehicle.

How does mounting height change what the camera actually sees?

Height and tilt set where the frame hits the ground. The near edge is the blind spot under the camera: height ÷ tan(tilt + vertical angle ÷ 2). The far edge is height ÷ tan(tilt − vertical angle ÷ 2), or unbounded when the top of the frame is at or above horizontal. The ground distance to the centre of the frame is height ÷ tan(tilt). That geometry assumes flat, level ground.