Night Moves: The Challenges of Noise and Blur
We’re fed up with the images we get from our few-year-old surveillance solution – it’s fine during the day but as soon as evening arrives we lose the fine detail to noise and blur.
We’ve also installed a higher resolution camera in a key location to get more detail and find at night for the above reasons we get even less detail than before! We also have IT bullets but their performance in monochrome leaves plenty to be desired in the real world. Is there a surveillance camera that gives court-admissible images at 5 lux or is this impossible for current technology?
A: Our testing shows that most cameras suffer from noise and blur under 10 lux. We favour noise over blur but there’s a law of diminishing returns. You should be able to get court admissible images at 5 lux out to 12 metres at 5-6mm focal lengths. You can increase the minimum shutter speed to reduce blur but the impact on image quality isn’t always clear cut. We would be using slightly longer focal lengths with cameras we were depending on at night. If we really needed faces we’d be provided some additional lighting, or leveraging existing ambient lighting.
All the top line box cameras will give you reasonable faces to 12m at around 5 lux but bullets are another matter. Given they are fitted with integrated IR, they are going to switch into night mode at around 10 lux. IT can be great in an unlit back lane but it might not be so effective on a city street with an average light level of say, 7 lux and lots of reflective surfaces. If your application is large enough to generate leverage, we’d be inviting some leading manufacturers to meet the demands of your application onsite.
It’s worth bearing in mind that higher resolution sensors tend to have smaller photo sites, which means they collect fewer photons and apply more amplification but making blanket statements about low light performance is very hard to do. Our experience is that lower cost high res cameras can suffer from blur in low light while some high end 4K cameras – the Sony VB770 is one – has outstanding performance in extreme conditions.♦