There are claims of extremely low light performance from surveillance manufacturers, yet we all saw at SecTech Camera Shootout this year that such claims don’t wash. What sort of performance would we be talking about if we can’t depend on specification sheets?
A: Many manufacturers claim to deliver crystal clear images in 0.01 lux unsupported by artificial light but typically these claims hinge on shutter speeds so slow you’d get serious motion blur. And there’s a point with low light performance where pushing ISO generates lashing of noise. Obviously, there’s a point of balance, but you’re not going to find that balance pulling default cameras out of their boxes and screwing them into the wall.
At SecTech we saw that 8-10 lux is about right for unsupported street surveillance applications. It’s not going to be perfect – you’ll get some motion blur and some noise, but it will do – especially with bigger sensor sizes and better designed camera engines. You can get situational awareness underneath this lux threshold, but you’ll only get face recognition at very close ranges – a couple of metres or so.
When using low light cameras try to match them with lenses with faster (smaller F number) apertures. For low light applications, a fast lens aperture like F0.95 or F1.2 is going to get more light to the sensor than a lens with an aperture of F2.8mm.
Something to bear in mind is that at default many cameras will step down to 1/30th of a second in gloomy daylight. That’s not ideal if you want moving plates and faces.
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