What’s The Best CCTV Focal Length For Face Recognition Applications Including Access Control?
What’s The Best CCTV Focal Length For Face Recognition?- Is there a CCTV focal length that offers the least possible distortion and the best field of view for the most reliable face recognition?
A:
A typical 1/1.8-inch sensor will have dimensions of 7.6 x 5.7mm meaning a slightly shorter focal length than you’d expect provides necessary perspective for an appropriate angle of view, while a 1/3-inch sensor with an area of 4.5 x 3.4mm will require a shorter focal length still to have the equivalent perspective which would approximate 50mm on a 35mm camera – a short-mid tele.
All other things being equal, smaller CCTV sensors do better in terms of perspective distortion than larger sensors, given a lens with the same focal length. Using a standard 2.8-9mm varifocal lens and a 1/3-inch sensor, the sweet spot is likely to be in the middle of the range at around 5-7mm where you’ll get an angle of view of around 50 degrees.
At this mid-point in the focal range you’ll get the least barrel distortion and the least pincushion distortion. A flatter image from a slightly longer lens is going to be more reliable in a facial recognition application.
Note that these speculations depend on factors like distance of the face from the lens to say nothing of image quality, which itself depends on many variables that may not be priorities for camera manufacturers any longer.
The latest solutions can recognise multiple faces in their angle of view but for access control applications reliability is going to be more important than lateral scope.
In fairness, there are plenty of ancillary security devices that seem to deliver reasonably accurate facial recognition performance using what often seem to be wide-ish angle lenses and typical resolutions of 4-5MP.
In access control applications demanding “most reliable” facial recognition, however, it’s higher standards will be required. We’d be talking to facial recognition providers directly to learn more.
Vix Vizion Imagus partners with multiple providers on facial recognition access control in ANZ – you can learn more here or read more SEN news here.
“What’s The Best CCTV Focal Length For Face Recognition Applications Including Access Control?”
