VID-09

Camera Distance (IEC 62676-4 DORI)

IEC 62676-4 · ANSI/AVIXA D401.01

01 · Camera

Sensor format

Focal lengthⓘ

Sensor resolution

02 · Scene

Distance to target

Camera mounting height

Target heightⓘ

Awaiting input6 fields left: Sensor format · Focal length · Sensor resolution · Distance to target · Camera mounting height · Target height

Capacity and layout

The drawing appears when the inputs are complete

01
Work out Detect, Observe, Recognise and Identify distances for a camera from its sensor format, focal length and resolution, and check pixel density and depression angle at a chosen target.
02
Tip. DORI is horizontal pixel density on the target, not megapixels on the sensor. Doubling the resolution only doubles the identification range if the lens still puts the subject across the same part of the frame — a wider lens gives most of that back.
03
25 px/m — Detect
04
62.5 px/m — Observe
05
125 px/m — Recognise
06
250 px/m — Identify

IEC 62676-4 DORI

DORI defines what a surveillance camera can actually deliver at a given distance, in terms of horizontal pixel density on the target rather than the camera’s headline resolution. The four levels correspond to four different operational questions, and specifying the wrong one is the most common and most expensive mistake in a surveillance design.

The four task levels

Each level sets a minimum horizontal pixel density on the subject. The distance at which a camera meets it falls as the lens gets wider, because the same pixels are spread across more scene.

Use cases

Detect 25 px/m — someone is present
Observe 62.5 px/m — clothing and characteristic detail
Recognise 125 px/m — is this someone seen before
Identify 250 px/m — positive identification

Formula

Pixel density = horizontal pixels ÷ scene width at that distance

IEC 62676-4

Field of view and distance

Scene width grows with distance and with the lens angle. Doubling resolution only doubles the useful range if the lens still frames the subject the same way.

Use cases

Scene width = 2 × distance × tan(HFOV ÷ 2)
Wide lenses cover more area at lower density
Telephoto trades coverage for identification range
Mounting height adds to the true optical distance

Formula

Distance = scene width ÷ (2 × tan(HFOV ÷ 2))

Rectilinear lens assumed

These figures assume a rectilinear lens and uniform pixel distribution. Real wide-angle lenses compress pixels toward the frame edges, and camera tilt foreshortens the target plane. For anything safety- or evidence-critical — facial recognition, licence plate capture, low light — add a 10 to 20 % margin in resolution or reduce the working distance to suit.