How CCTV Night Vision Works

There are as many different approaches to CCTV lighting solutions as there are types of surveillance cameras. Any number of approaches can be used to illuminate a scene with thanks to the range of technologies we have today. Over time, these solutions have evolved to become more affordable, accessible, and practical in a surveillance setting. Each solution has its own advantages & disadvantages, but all play key roles in the CCTV camera landscape. In this article, we’ll have a look at some of the major ‘Night Vision’ solutions being used and how they compare to each other.

Low-Light Solutions

There’s no single do-it-all solution for low-light surveillance. Factors like ambient lighting levels, light intensity, the type of light source (natural vs artificial), security requirements, etc, can greatly vary between environments. Depending on requirements, certain low-light solutions can become unusable, or even combined with other technologies. As such, the best solution for the job also tends to change between different environments.

Infrared light (IR)

Infrared lighting is by far the most popular approach used to solve the issue of lighting. It’s cheap, simple, and effective. Generally speaking, an ‘IR’ camera will have a built in LED that produces Infrared light, which is invisible to humans. The camera, however, can see this light and use it to illuminate a dark environment. Have a read of our article on IR Cameras for more information.

Supplementary IR lighting can fully illuminate most scenes without needing other natural/ambient light sources. Thanks to the simplicity of this technology, using IR lighting can be a very reliable solution for most applications. IR tech also tends to be the most readily available and has one of the lowest costs. This makes it a popular choice for indoor surveillance (or where there is no natural light), residential CCTV systems, small businesses, and most other urban environments.

Using supplementary IR light does of course have its own weaknesses. Firstly, the range of the built in IR LED has its limits. As with visible light, the IR light’s intensity exponentially drops off with distance. This often makes it unsuitable for surveillance of large/expansive environments like parklands, railways, roads, etc. Built-in IR lights can also make it hard for cameras to find appropriate exposure levels. This will sometimes make objects closer to the camera appear overexposed and washed out, while the background is underexposed and too dark.

It’s worth mentioning that powerful IR lights can also damage eyes in the same way that visible light can. Some powerful IR setups that use lasers to project light, or those with ranges of over 150m risk permanently damage eyesight if placed carelessly.

Passive IR

The term “Passive IR” describes a few techniques that use the natural or ambient light to illuminate a scene, rather than actively producing light. Around 54% of the energy produced by the sun is given off as infrared light, while visible light only accounts for 39%. Almost all cameras filter out IR light because of how it interferes with image quality and colour balance. Day/Night cameras like those with passive IR tech switch over to let infrared light in at night, allowing it to see significantly better in low-light conditions.

Passive IR cameras are not the most common solution for low-light environments, but play an important role in night vision technology. These surveillance cameras require no additional lighting other than existing natural/ambient light. This eliminates many of the issues present in active IR cameras. Passive IR cameras are also harder to detect, are safer than active IR surveillance systems, and can see in full colour. This makes them a popular choice for outdoor areas like parklands, roadways, or areas with reliable ambient lighting.

The single largest disadvantage of passive IR systems is the inability to see in complete darkness. This makes them unsuitable for most indoor environments like offices, warehouses, small businesses, etc. These CCTV cameras are also more susceptible to environmental influences. Unexpected cloud cover and other such changes in ambient/natural light can impact performance.

Thermal Cameras

Thermal cameras use the thermal radiation (i.e. the ‘heat’) given off by an object to produce an image. Everything naturally emits some amount of thermal radiation, so these cameras don’t have to rely on reflected light to see. This gives thermal CCTV cameras a range of unique applications and advantages over normal surveillance systems that use visible or IR light. Thermal cameras are often combined with normal cameras to give operators more information and better context for thermal images.

Thermal CCTV cameras are immune to many of the visual artefacts and issues present in standard CCTV cameras. Obstructions like smoke or rain would normally cripple a camera’s surveillance capabilities, but have virtually no impact on thermal cameras. Inherent issues with conventional CCTV cameras like over/under exposed footage, lens flares, dark zones, grainy footage, etc, are also completely eliminated. This gives them exceptional low-light performance in both indoor & expansive outdoor environments. Additionally, thermal cameras are arguably the most reliable and consistent night-vision solutions commercially available.

The downside to this technology is the increased cost. Surveillance cameras with thermal modules are generally out of reach for most DIY installations, home security systems, and small businesses. Due to this cost, CCTV thermal technology is often limited to higher-end cameras or cameras designed for specific applications.

Mechanical Enhancements (Aperture, Shutter Speed, CMOS Sensor, etc)

While technologies like IR and thermal vision tend to get the spotlight, the smaller mechanical enhancements are often the true backbone for NV technology. ‘Mechanical Enhancements’ refers to the design of the internal camera components like the aperture size, shutter speed adjustments, CSMOS sensor size, lens quality, etc. In a recent article, we looked at the importance of apertures in the low-light surveillance. Physical components like these serve as the underlying solution for many low-light technologies like Hikvision’s ColorVu and DarkFighter cameras.

Hikvision ColorVu is capable of surveillance in very low light levels while still producing full-colour footage. It does this by using an extra-large aperture size, combined with other enhancements like a larger CMOS sensor, anti-reflective lens coatings, etc. By adopting multiple smaller enhancements, this essentially gives the camera strong low-light performance.

Mechanical specs vary greatly from camera to camera, and can affect the low-light performance in any number of ways.

Software/Digital Enhancements (BLC, HLC, 3D DNR, Noise Suppression, etc)

By itself, digital enhancements to footage are not enough to give standard cameras NV capabilities. Instead, they work in conjunction with other physical enhancements to raise the overall low-light surveillance quality. These technologies take the raw video data produced by the CCTV camera and use a range of simple adjustments, complex algorithms, or AI techniques to make footage more usable.

Such enhancements are relatively standard between cameras and different brands thanks to the ease of implementation. This means that the software found in high-end CCTV cameras is often the same as that found in more affordable alternatives. Most different cameras will also include the same types of enhancements like noise suppression, low-loss codecs, 3D DNR, etc.