Tools / Pixels on target
Pixels on Target & DORI Calculator
Assumes a rectilinear lens and a target near the image center, square to the camera. The default target is a 1.7 m standing person.
The target as the sensor sees it
—DORI ranges with this lens · line marks your distance
IEC 62676-4 pixel density levels
Pixel density is measured across the target in pixels per meter. Detect, observe, recognize and identify (DORI) are the four levels most security specifications quote; monitor and inspect bracket them. The two right columns use your sensor, lens and distance.
| Level | Pixel density | What you can tell | Max distance | Focal length needed |
|---|
Formulas
For a rectilinear lens, pixel density at distance D on the optical axis is PPM = f / (p · D), with focal length f and pixel pitch p in the same units as D. Millimeters per pixel is 1000 / PPM, and pixels on a target of size T is PPM · T.
The maximum distance for a level is D = f / (p · PPM), and the focal length that reaches it at a distance is f = PPM · p · D. Scene width is Nx · p · D / f. Off-axis targets get slightly fewer pixels, and lens distortion, compression and motion blur all reduce the usable detail, so leave margin above the threshold.
Background reading: DORI explained: pixel density for security cameras