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How does night vision security camera work?

by | Oct 15, 2018 | Learn

When selecting a security camera to protect a home or business, there are couple of features to consider. These include but are not limited to image resolution, the size of the image sensor but most importantly, the night vision.

Night vision is an integral part of a security camera. Night vision cameras have been around for over 3 decades and they have gone through many improvements. It is the ability for a security camera to see in a pitch-black or at twilight.

Since criminals love to carry out their nefarious activities at night, it is therefore necessary to use a night vision security camera such as Amcrest 960H or Zmodo Wireless Outdoor Cameras

Table of Content

Types of Night Vision

There are three basic types of night vision technology in security cameras.

– Low-Light Night Vision

This can also be referred to as image intensification. Technology has upgraded from what it used to be in decades. Low-light night vision relies on image intensification technology to deliver a coloured night vision in a very low light atmosphere.

image intensification technology security camera

The image intensifier is a vacuum-tube based device, i.e. photomultiplier tube that can generate an image from a very small number of photons such as the light from stars in the sky, so that a dimly lit scene can be viewed in real-time by the naked eye via visual output, or stored as data for later analysis.

image intensifier technology schema

When light strikes a charged photocathode plate, electrons are emitted through a vacuum tube that strike the microchannel plate that cause the image screen to illuminate with a picture in the same pattern as the light that strikes the photocathode, and is on a frequency that the human eye can see.

The image is said to become “intensified” because the output visible light is now brighter than the incoming light. However, these cameras still need some light available to produce a colour image.

Color Night Vision compared to Infrared Night Vision

Benefits of low-light night vision camera

  • Even though low-light cameras require some visible light in order to record, they still remain the best because they outperform IR night vision cameras. They are the only security cameras that are able to produce a colour image in a low light level conditions.
  • They are affordable.

– Infrared (IR) Night Vision

Infrared (IR) light was first discovered in 1800 by Sir William Herschel.

light wave spectrum

It is an invisible band of radiation at the lower end of the visible light spectrum. With wavelengths from 750nm to 1mm, infrared starts at the end of the microwave spectrum and ends at the beginning of visible light. Infrared light has a range of wavelengths that starts from red light to violet.

Sir William Herschel split light into a rainbow (called a spectrum) by passing sunlight through a prism, and then placed a thermometer in different colours in that spectrum.

Circumstantially, he found the thermometer showed a rise in temperature, even when placed in the dark area beyond the edge of the red light. He theorised that there must be more light beyond the colour red that we could simply not see with our own eyes.

Infrared leds on a security camera

Most security cameras now come with built-in infrared LEDs to provide night vision in low light or no light condition. But one of the most important features of an Infrared security camera is the Infrared Cut Filter or Infrared Cut Removable.

What is Infrared Cut Filter?

An Infrared cut filter is a mechanical shutter design. It is a piece placed between the lens and the image sensor. It’s being controlled by a motor or an electromagnet.

Infrared cut filters on leds

Infrared cut filters are used with colour CCD or CMOS cameras to produce accurate colour images. An IR cut filter blocks the transmission of the infrared light while passing the visible light. As modern CCTV cameras all have a wide visible spectrum, they can all see IR light to some degree.

When the infrared cut filter is activated, it will block infrared light and allow only visible light to pass through. When the ICR is turned off, infrared light will be allowed and images will turn into black and white mode.

Infrared cut filter getting removed

The infrared cut filter is being controlled by light sensor on the security camera. At twilight, the light sensor simply sends a remove signal to the infrared cut filter so that more light could reach the image sensor of the security camera. This way, black and white image is produced.

However, precaution has to be taken if installing an infrared security camera in the room through a glass window. Infrared security camera can be affected by glass reflection or window glare at night, which could cause the video being washed out by overexposure of lights at night.

over exposed infrared camera image

Make sure to turn off the infrared LEDs and any other LED indicator on the security camera. You can check Amcrest camera reviews and comparison to choose any camera which you can install through a glass window.

Amcrest IP cameras give the users option to set the camera infrared to “auto” or “off” after logging into the camera through a browser. This way, you can completely turn off the camera infrared light from blowing out the image.

Mixed reactions have always been trending on whether motion detection will work through a glass or not, since security camera sense motion by comparing pixels within the video frame, motion detection will definitely work.

However, the security camera has to be installed not far away from the glass window. The distance should not be more than 1ft, otherwise it becomes less effective.

It is also needed to check the window frame to make sure it is not obstructing the view of the camera lens.

Benefits of infrared night vision security cameras

  • Unlike low-light night vision cameras, IR cameras give users opportunity to record in a pitch black condition without additional light. The cylindrical shape infrared LEDs provide infrared illumination at night for the camera image sensor to capture an image.
  • IR cameras are the cheapest security cameras on the market, they do use much less energy and they are also very efficient.

– Thermal Night Vision

Thermal night vision camera features a unique lens that allows infrared energy to pass through it. Then the focus light hits a sensor that scans the information and draws from several thousand points in the field of view.

Through this process, an intricate temperature pattern known as a thermogram is created, which only requires one to thirtieth of a second to develop. The thermogram then transforms into electric impulses, which are directed to a signal processing unit that translates the information into data for the visual.

The created image displays as various colours that correlate to the amount of infrared energy emitted. It is this combination of elements that generate the image that emergency professionals rely on to protect people as a first use.

Thermal night vision uses heat to see instead of intensifying light like low-light night vision camera. Unlike low-light night vision and infrared night vision, thermal night vision can see no matter the light level.

Thief captured on Thermal Night Vision

Even in total darkness and poor weather conditions, thermal imaging technology allows users to detect and see at great distances. The ability to see image over a longer distance gives thermal night vision a distinct advantage over it counterparts.

Thermal cameras see heat instead of light. The more heat an object generates, the more thermal contrast it gives and the easier it is to see on screen.

Everything on earth has a certain heat. People, animals and car engines generate especially a lot of heat. This is why it’s easy to see them with an thermal night vision even if the atmospheric conditions are really bad (for example, if smoke, rain, or fog is present).

People captured on a thermal night vision camera

Whether the light levels are too low, too high or become oversaturated, thermal security cameras are not affected. They can see through anything.

Benefits of thermal night vision cameras

  • Thermal security camera is the only solution to address a visible image contrast to see at night. When a target is brighter than its surroundings, it has good visual contrast and it is easy to see. When a target doesn’t have a good visual contrast, you can’t distinguish it from its surroundings. There is no night vision camera that can reveal contrast that is just not there.
  • Unlike other night vision cameras, thermal security cameras are completely immune to smoke, dust, and anti-CCTV surveillance devices like reflectacles glasses, visor glasses, infrared laser glasses.
  • Government agencies, security companies as well as large corporations rely on thermal security cameras for many security applications because they eliminate false alarm.

To conclude about night vision for security cameras.

Night vision security cameras are excellent tools and are mandatory if you want to have a complete video surveillance security system. It is important to choose the adapted night vision cameras to complete your security setup.

Video surveillance systems without night vision cameras aren’t useful at all. Unfortunate events tend to happen at night or in the dark. Only a security camera that has a built-in night vision technology will be able to capture an image at night, which can then be used as an evidence.