Video surveillance in low-light conditions, at night, during thunderstorms or in covered environments for example, has always been a problem for the industry. Initially we would have to install white or IR lights (on the camera or independently) to get footage in the dark, and then thermal cameras offered an expensive solution, but with poor resolution.
Today, camera vendors have improved the technology in their devices to offer colour images in various stages of darkness, with some even claiming that their systems work in complete darkness. Initially these claims were treated with realistic scepticism, but low-light technology has improved impressively over the years.
Smart Surveillance asked a number of camera manufacturers for some insight into their low-light offerings, including additional lighting options for the best views. Responses were received from:
• James Xie from Dahua Africa.
• Hunter Ye from Hikvision South Africa.
SMART Surveillance: Is there increasing interest in low-light cameras in general? Are there specific market sectors or areas where these cameras are more popular? In addition, are low-light cameras replacing thermal cameras, or are both used in different cases?
Dahua: Full colour technology has grown in popularity over the years, ensuring users 24/7 colour monitoring as well as trustworthy performance in terms of clarity, definition, flexibility, accuracy and intelligence. Full-colour cameras can replace thermal cameras for some scenarios such as perimeter protection.
Thermal cameras, which do not require a light source, are excellent for providing enhanced coverage in diverse environments, such as those with harsh conditions or extreme darkness. In addition, thermal cameras have long range detection and temperature measurement capabilities, allowing them to be used in conjunction with visible light cameras to achieve all-weather monitoring and comprehensive surveillance.
Hikvision: Yes, there is an increasing interest in low-light cameras. Hikvision partnered with an Asian publication in running a survey about low-light cameras a few months ago, with 73% of respondents indicating that they saw a rise in market demand for low-light cameras compared to the year before. This is on par with findings from research reports on the topic. Omdia previously released findings that projected a rapid rise to 51 million, of video security cameras equipped with advanced low-light functionality in 2022, more than 10 times the number of such cameras in 2015 (4.75 million).
According to the survey results, the majority of the current low-light camera installations are concentrated in two specific verticals: commercial (22%) and residential (22%), with small businesses (19%) following close behind.
However, we don’t think low-light cameras are replacing thermal cameras, as they have different strengths and are suitable for different application scenarios.
SMART Surveillance: What factors should the end user be on the lookout for when selecting a low-light camera?
Dahua: After Dahua introduced the low-light concept, we continued to add full colour, and smart dual light concepts to our systems. For example, if the monitoring scene has a sufficient light source, you can choose low-light products, and if the scene does not have a light source, you can choose full colour products for regular monitoring and supplemental lighting. If the user does not want to have obvious white light pollution but wants to monitor the event with a full-colour picture, you can choose our smart dual-light products. It can be switched on to obtain full-colour detailed images according to a trigger set when people and vehicles appear in the scene.
Hikvision: There are six factors that we suggest end users look out for when selecting a low-light camera.
1. The selection begins with the type of low-light camera the user wants to get. Currently, there are mainly three types of low-light camera – IR camera, which switches to black-and-white mode at night; low-light camera, which captures colour 24/7; and a regular security camera with supplemental lighting. Each has its benefits and can be applied in different applications.
2. End users should consider the type of supplemental lighting that they want to use: Should it be white light, IR light or hybrid? Again, this depends on the user’s own case. White light can be deployed on streets, yards and other outdoor open areas where users don’t find the light annoying. IR light, on the other hand, is unnoticeable and can be applied in virtually all scenarios. The downside, of course, is it delivers black-and-white images, and important colour details may be lost.
3. End users should also ask themselves what the lux rating is for the low-light camera. The lux rating of a security camera refers to the level of illumination under which the camera can produce a good image. For quick reference: illumination under direct sunlight measures up to 100 000 lux, whereas office lighting might be around 500 lux and a moonless, cloudy night 0.0001 lux. Basically, the less light, the lower the lux number.
4. When it comes to image sensors for the best low-light security cameras, size matters. Many people would think that higher megapixels directly equate to better image quality, but a lot of different factors come into play. With the resolution being equal, a larger sensor works better as the larger sensor can gather more light and generate a brighter image.
5. When choosing a low-light camera, what form factor should the user get – bullet, dome or PTZ? It depends on the monitoring distance and environment. For 60-metres and above, a PTZ is recommended. For monitoring within 60 metres, dome/turret form factors are recommended for indoors and the bullet form factor is recommended for outdoors.
6. They can also consider if they need analytics on their low-light cameras. The use of video analytics in low-light cameras have been gaining popularity in the past few years, enabling features like object and motion detection and real-time alerts. Human and vehicle classification is very practical on low light cameras. With analytics, users can detect and retrieve clear human and vehicle targets at night.
SMART Surveillance: What technical features do your company’s low-light cameras include to make them work as required?
Dahua: Dahua Full-colour network cameras offer dual-lens, 4K colour images, vari-focal lenses, and AI features that can significantly optimise surveillance monitoring and greatly benefit end users in terms of clear, colour image output.
Dual-lens camera: We offers dual-lens cameras with large F1,0 aperture that collects 2,5 times more light compared with the F1,6 aperture. Its Dual Light Fusion capability allows the camera to collect visible colour details and light information using separate lenses. These cameras are equipped with dual CMOS (1/1,8-inch and 1/2,8-inch), providing a 36% increase in brightness and 14 times increase in S/N ratio. With pixel-level frame-by-frame mapping, these dual-lens cameras present high image definition and colours even when the supplementary white light is off, thus reducing light pollution and the attraction of insects that can adversely affect the monitoring of the scene. What’s more, by utilising the high precision AA (Active Alignment) process, the lenses and sensors of these cameras are all precisely aligned, ensuring that the scene is captured and restored clearly and accurately.
4K colour images: Details and colours are two essential elements in surveillance monitoring. They can be used to detect and recognise targets helping to prevent any possible incidents or events. The 4K network cameras of Full-colour 2.0 are equipped with a 1/1,2-inch image sensor. Compared with conventional 8 MP camera, this image sensor significantly increases the pixel size by 110%, allowing it to capture real-time 4K colour images even in low-light conditions. In addition, these Full-colour 2.0 cameras also boast 42% increase in brightness, and 400% increase in S/N ratio, providing a clear and high-quality image of the monitored scene.
Vari-focal lens: Full-colour network cameras adopt motorised vari-focal lenses with approximately 5X optical zoom and auto focus function that can maintain clear details of the monitored scene even after zooming in. It solves the difficulty of capturing vivid colour details of targets during the night or in environments with low illumination, which is a common pain point when using traditional IR vari-focal cameras. It covers narrow indoor spaces and wide outdoor scenarios and makes operation more convenient and greatly saves time and labour costs.
AI features: Full-colour network cameras can work with Dahua’s 5-I/L series NVRs, which enable colour searching for human and vehicle targets and allows for the extraction of relevant video footage. It includes the colour of the person’s clothes (top and bottom), as well as the colour of the car exterior. Additionally, another AI feature of this camera series is its AI Schedule that allows users to set different AI functions according to the time schedule, providing more flexibility in monitoring and greatly reducing operation costs.
Hikvision: Hikvision’s ColorVu and DarkFighter technologies provide full-colour footage 24-hours a day, so users see the same sharply rendered images at night as they would see in broad daylight. Now boosted by Super Confocal Technology, their performance in low lighting is even more stable and precise. This is a high-calibre-lens design which reduces optical light dispersion to ensure that the point of focus on the sensor for the infrared light is virtually the same as that of the visible light (thus, ‘con’-focal). Focusing both types of light at the same spot helps prevent blur and improves the user’s viewing experience by rendering clear, vivid images both in colour and black-and-white. Achieving confocal imaging with F1,0 super aperture is also an industry-first.
Hikvision’s Smart Hybrid Light technology can automatically switch from IR light to visible white (supplemental) lighting at night. Equipped with this technology, cameras offer three supplemental lighting options to suit a user’s unique night-time scenario, depending on the need. The white or visible light mode establishes colour imaging; the IR mode (invisible to humans) enables continual black-and-white imaging at night with no light pollution; and the ‘smart’ mode enables the light to automatically change between the two modes based on perimeter events.
SMART Surveillance: One of the challenges about low-light cameras is that they have a more limited effective distance when light is poor, what is your company doing to get the best images over longer distances?
Dahua: Light conditions do have a very direct effect on the outcome of the image quality. So, for low-light cameras we have not only a large 1/1,8-inch target sensor, but also an increased aperture size of F1,0, both of which ensure good full-colour results even in low light conditions. For low light conditions at long distances, especially at distances of more than 50 metres, we would recommend the use of a thermal imaging device, which is after all practically unaffected by ambient light.
Hikvision: For long-distance video monitoring, a sensor with large optical format and a lens with large aperture are used, in addition to supplemental lighting.
Hikvision’s DarkFighterX technology uses a large lens aperture and dual sensors to capture and combine visible-light video images and images based on Infrared perception. When data from the two sensors are combined using a technology called ‘Bi-Spectral Fusion’, the result is high-definition, full-colour video imaging, even in conditions of near-total darkness. This kind of video is sharp enough to capture the licence plates of vehicles traveling at speed, even after the sun goes down.
SMART Surveillance: With the additional noise in low-light cameras, even with noise reduction, are your analytics/AI algorithms able to provide reliable results in poor light conditions?
Dahua: With regard to noise in low light conditions, we have added 3D NR to most of our products to ensure that the noise problem is reduced, and a clean picture is obtained.
Hikvision: Yes, our AI algorithms are able to provide reliable results in poor light conditions. For example, Hikvision AcuSense technology uses AI algorithms to distinguish between people, vehicles, and other moving targets such as rain, leaves and animals. When motion is detected, the system analyses whether or not it is associated with a human or a vehicle, and whether an alarm should be triggered. This means alarms are only triggered when pre-set intrusion types are detected, allowing security teams to focus on the real threats and act.
Combining this technology with our ColorVu low-light imaging technology, cameras are able to deliver clearer, vivid colour images, helping operators to see the scene clearly. The addition of AcuSense technology means that they can understand more readily what they are looking at, and automated alerts have a far lower false alarm rate, with more than 98% alarm accuracy.
SMART Surveillance: What are the latest low-light offerings available from your company and what other advice would you give to users deciding if they should invest in these cameras?
Dahua: Dahua is always investing in innovation and the exploration and development of full-colour products. We have now launched our latest Full-colour Cube range, which includes full colour, Smart Dual Light and 3-in-1 cameras. And we have also derived a supplement with high resolution (to 4K) and a 180° ultra-wide angle duo lens camera.
Hikvision: The ColorVu cameras with Smart Hybrid Light, and DarkFighterX cameras are our latest low-light offerings. The products are ideal for both indoor and outdoor scenarios, such as warehouses, retail stores, public parks, and residential settings where little or no movement is expected at night but discretion is desired for security cameras. Smart, automated lighting options combined with accurate and sharply focused details creates a camera that goes above and beyond current security industry expectations and performance.
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