Convert rated angles and sensor size into coverage width and pixel density for each focal length, with lens thresholds for pinhole cameras in kiosks, cabinets and indoor points.
Angle Comes from Focal Length and Sensor Size Together
On the same sensor a shorter focal length gives a wider angle: coverage grows but the pixels available per unit distance fall. Most miniature cameras here use M12-mount fixed-aperture lenses at F1.4, and angles are labelled either as a single value or as diagonal by horizontal by vertical. The 2MP starlight pinhole AHD micro camera VDC-MC01F20NS rates its 3.7 mm pinhole lens at 79°, and the 30×30 mm board model VDC-MC04F20NS-30 with a 3.6 mm lens is also rated at 79°.
The same focal length gives a different angle on a different sensor size. The 1/2.9-inch black-light full-colour 2MP AHD micro camera with a 2.8 mm F2.2 lens is rated 140° diagonal, 116° horizontal and 60° vertical. On the 12MP AI waterproof bullet, the CS-mount 8 mm F1.8 lens on a 1/2.5-inch sensor gives 50.7° diagonal, 44.4° horizontal and 32.6° vertical. The 3MP starlight waterproof dome uses a 2.7 to 13.5 mm manual zoom that narrows from 93° to 28.7°. The 8MP 10x motorised zoom bullet runs 5 to 50 mm and pulls its horizontal angle in from 50.85° to 7.67°. Convert using the horizontal angle as labelled on the product.
Converting Horizontal Coverage Width
Coverage width follows from geometry: W equals 2 times the viewing distance times tan(horizontal angle divided by 2). The table applies several horizontal angles actually labelled on products to different distances, rounded to one decimal place, so you can check directly whether a point covers its corridor.
| Horizontal angle | 3 m | 5 m | 10 m | 20 m | 50 m |
|---|---|---|---|---|---|
| 116° (2.8 mm wide-angle micro camera) | 5.8 m | 9.6 m | 32.0 m | 64.0 m | 160.0 m |
| 84° (thermal camera visible channel, 4 mm) | 4.2 m | 7.0 m | 18.0 m | 36.0 m | 90.0 m |
| 79° (3.6/3.7 mm micro camera) | 3.9 m | 8.2 m | 16.5 m | 33.0 m | 82.4 m |
| 58° (explosion-proof camera, 6 mm) | 2.9 m | 5.5 m | 11.1 m | 22.2 m | 55.4 m |
| 44.4° (12MP camera, 8 mm) | 2.2 m | 4.1 m | 8.2 m | 16.3 m | 40.8 m |
| 31.4° (12MP zoom at the telephoto end) | 1.5 m | 2.8 m | 5.6 m | 11.2 m | 28.1 m |
| 7.67° (8MP 50 mm telephoto end) | 0.4 m | 0.7 m | 1.3 m | 2.7 m | 6.7 m |
Pixel Density and Decision Thresholds
Coverage width decides how far the same pixel count stretches: divide the horizontal pixels of the picture by the coverage width to get pixels per metre. A 1920-pixel-wide model at a 79° angle yields about 233 pixels per metre at 5 m, about 116 at 10 m, about 58 at 20 m and about 23 at 50 m. Industry practice uses four experience bands, detection, observation, recognition and identification, at roughly 25, 60, 125 and 250 pixels per metre.
That gives thresholds you can act on. A 3.6 mm or 3.7 mm lens on a 1080P micro camera sits near the recognition band within 10 m and reaches only observation at 20 m. To hit the identification band of 250 pixels per metre at 10 m, the horizontal angle must close to about 44° or below, which means switching to a 6 mm or 8 mm lens. The quad-format starlight micro camera VDC-MC02F20NS offers 3.6, 6 and 8 mm options, and the 12×12 mm VDC-MC08SL provides six focal lengths: 3.7, 3.6, 6, 8, 12 and 16 mm. Read the table above backwards by distance to fix the band.
Mechanical Constraints on Micro Cameras
On a miniature camera the body size limits the lens before the angle does. The formats seen most often are the slim 80×Φ20 mm, the board types at 30×30×14 mm and 40×40×14 mm, the Φ25×80 mm network micro bullet, the 20×20×28 mm black-light full-colour model, and the MC08SL at only 12×12×6 mm, which runs on DC3.3V ±10% and needs an external driver or a step-down circuit.
Pinhole and non-pinhole versions sit close on angle: the 3.7 mm pinhole lens and the 3.6 mm board lens are both rated 79°. They differ in cut-out and mounting, not in coverage. For self-service kiosks, display cabinets, checkout counters and equipment cabinets, look up the measured distance to the target in the table above to set the focal length. Capture inside a cabinet usually falls between 1 and 3 m, where the wide end frames the operator's movements more easily.
Night Illumination and the Lens
The IR row on micro cameras mostly reads Null or Color, meaning the body carries no illuminator and night imaging depends on site light. An F1.4 fixed-aperture lens still forms a colour picture at 0.001Lux colour sensitivity, provided some ambient light reaches the point. A cabinet interior with no light at all needs a separate white-light or IR board, and the IR board and cable length can be adjusted at the customisation stage.
Network models with IR need protection against near-field overexposure. The 3MP starlight bullet's 42 IR LEDs cover 35 to 40 m, and the 8MP fixed-focus bullet's 36 LEDs cover 20 to 30 m. When the target stays within 2 m for long, the frame centre washes out and loses detail. Options are to switch to a full-colour low-illumination model, adjust the tilt so the main illumination falls behind the target, or mask and attenuate the front of the illuminator.
Focal Length Customisation and Confirmation
Send the measured distance from the point to the target, the action or feature that must be legible, the coverage width you can tolerate, the body cut-out size and the recorder model to info@vctcctv.com, or call +86-755-28146081. We recommend a focal length from the conversions above and state whether a custom lens is needed. Shenzhen VIDCOM Technology Co., Ltd. was founded in 2012 and its own production line supports OEM customisation of lens focal length and firmware parameter presets.
