The four standards
| Purpose | Subject height | What it gives you |
|---|---|---|
| Identification | 100% of screen height | Enough facial detail to identify a stranger |
| Recognition | 50% | Enough to recognise someone you already know; also the standard for a vehicle and its plate |
| Observation | 25% | Clothing, actions and movement, not the face |
| Detection | 10% | That a person is there, and where they go |
These are the figures used in the CCTV operator qualification and they come from the police and Home Office guidance on CCTV picture quality. They are about the subject's height relative to the picture, not the camera's resolution: a 4K camera 80 metres away still gives you a detection image. Zoom, camera placement and lens choice are what change the percentage.
Using it in the control room
- Before you capture an evidential image, check the size. If you need identification and the face is a third of the screen, zoom first.
- When you cannot get identification from one camera, note what you can get, for example recognition on camera 4 and observation on camera 6, and say so in your statement.
- For vehicles, the recognition standard is what makes a plate readable; record the plate in the vehicle description builder order.
- Log the camera number, time and the image size you achieved. It goes in the audit trail with the time offset of the recorder.
This is assessed in the control-room practical on the SIA CCTV Operator course. See the CCTV practical guide for the full checklist.
FAQ
What is the identification standard for CCTV images?
The subject must fill 100 per cent of the screen height so there is enough facial detail to identify a stranger. Recognition needs 50 per cent, observation 25 per cent, detection 10 per cent.
How big does a vehicle need to be on a CCTV image?
Fifty per cent of screen height, the same as recognition, so the make, model and registration can be read.
How many pixels tall should a face be for identification?
At 100 per cent of a 1080-pixel picture, 1080 pixels; at 720 pixels, 720. Use the resolution selector above for other screens.