How do they produce a colour image at night?
They rely on two things: a wide-aperture lens that gathers as much available light as possible, and usually a soft built-in white light that comes on when needed. So instead of switching the colours off and turning black and white under infrared, the image stays in colour as long as there is a minimum of light.
The difference from infrared (IR)
An ordinary IR camera switches the colours off at night and gives you black and white, but it works in complete darkness. A colour night-vision camera keeps the colours but needs some ambient light (street lighting or a dim lamp) or relies on its own white light. The essential trade-off: colour against working in absolute darkness.
When it justifies the difference
- Entrances and cash-handling points: where the colour of clothing and of a vehicle is important evidence.
- Shopfronts and streets: usually with enough ambient light for it to work in colour.
- Shops and facilities under a requirement: where precise identification of people is expected.
When you do not need it
In a place that is completely dark with no ambient light, a colour camera falls back on its own white light, which may not suit every site (it draws attention). And in internal corridors or places where colour does not matter, an ordinary IR camera is cheaper and does the job. Do not pay the colour premium where you will not benefit from it.
In short
Colour night vision is an excellent investment at the sensitive points that have ambient light (entrances, shopfronts, the till), and an unnecessary luxury at internal or completely dark points. The best answer is a mixture: colour where colour matters, and IR where IR suffices.
