Camera Max Distance for a Pixel Density (DORI)
The farthest distance a camera still meets a target pixel density (a DORI task).
Example
You enter
- Sensor width (mm, e.g. 1/2.7in = 5.37) 5.37
- Focal length (mm) 4
- Horizontal resolution (pixels) 1920
- Target pixel density (ppf, 76 = Identify) 76
You get
- Max distance for that density 18.818
- Fov (deg) 67.74
Checked against published worked examples from: Theia Technologies (M. Peterson), via SDM.
Details, formula, and sources
Scopedistance = px x focal / (target ppf x sensor). A 1920 px camera with a 4 mm lens on a 5.37 mm sensor holds 76 ppf (Identify) out to about 18.8 ft; drop to 38 ppf (Recognize) and it doubles to 37.6 ft. Answers 'how far can it Identify' instead of the density at a set distance. FOV is fixed by the lens. A design aid; verify against the lens chart, low light, and a live view.
Formula or tablemax_distance = h_pixels x focal_length / (target_ppf x sensor_width), the inverse of ppf = h_pixels / (distance x sensor_width / focal_length); fov = 2 x atan(sensor_width / (2 x focal_length)); DORI band by ppf (8 Detect / 19 Observe / 38 Recognize / 76 Identify).
Source and editionIEC 62676-4 (Video surveillance systems - Application guidelines) DORI criteria, by name, solved for the distance; first-principles thin-lens field-of-view geometry.
Free accessThe FOV and scene-width geometry is first-principles optics; the DORI pixel-density bands are published in IEC 62676-4 (and widely reproduced by camera manufacturers).
What governsEstimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
API field namessensor_width_mm, focal_length_mm, h_pixels, target_ppf, max_distance_ft, fov_deg
- Thin-lens density max distance = px x focal / (target ppf x sensor); fov = 2 atan(sensor / 2 focal)first-principles optics
- DORI bands 25 / 63 / 125 / 250 ppm (~8 / 19 / 38 / 76 ppf) for Detect / Observe / Recognize / IdentifyIEC 62676-4
- Verify on site effective sensor width, lens distortion, and low light shift the real result; confirm with the lens chart and a live viewscope of this tile