A Quick Background

Color and black and white cameras both have their unique strengths for surveillance needs. Color cameras have the obvious benefit of providing the detail of…color. Being able to record the color of a suspect’s skin tone, clothing, or vehicle is beyond import – it can truly make the difference between solving the crime and the bad guy going free.

In order for color cameras to accurately produce colors, during manufacturing an IR cut filter is placed over the imager. The cut filter allows the camera to only see light in the visible spectrum (400 nm to 750 nm). Consequently, color cameras fall short when it comes to producing usable images in low light scenarios.

Conversely, black and white cameras don’t use an IR cut filter because they do not need to see color. With the absence of this filter, B&W cameras can make use of other light frequencies – such as infrared – which come from a variety of sources, including the sun, fluorescent lights, incandescent lights and of course… infrared illuminators.

As a result, B&W cameras perform significantly better in low light, and some can see at light levels as low as 0.0001 lux (almost complete darkness). An additional benefit of B&W cameras seeing in the infrared range is the ability to illuminate an area with IR, providing the camera with ample lighting while leaving the area naturally dark which can aide in the capture of suspects.

The Benefits of Day/Night Cameras

Day/Night cameras offer the unique advantages of both color and black and white cameras. D/N cameras work just like color cameras during the day and switch to a B&W mode at night, using a removable IR cut filter. As daylight fades, day/night cameras sense the lower light levels and mechanically remove the IR cut filter, instantly switching to a more sensitive black and white mode.

Day/night cameras are available in all shapes and sizes to meet virtually every application need. Beyond dome, fixed security and bullet cameras, D/N technology is also available in tiny board cameras – which are especially useful for undercover operations that typically happen in a wide variety of lighting conditions. Many day/night cameras also offer built in infrared illumination, making a very nice turn-key camera package.

The traditional and most effective D/N cameras are often referred to as true day/night cameras, and use a removable mechanical cut filter, as described above. However, digital day/night cameras (or electronic day/night cameras) are also available, which electronically adjust colors during the day, instead of using an infrared filter.

This allows the digital day/night cameras to deliver similar benefits of true day/night cameras, but at a lower cost. Without the need for a physical filter, digital day/night technology can also be leveraged for smaller form factors, such as bullet cameras.

Regardless of the type of day/night camera you choose, I recommend considering the following areas to ensure you get the very best solution for your application:

1. Lux ratings – Unlike traditional cameras, day/night cameras typically have two lux ratings – one for the camera’s color mode, and one for its black and white mode. Understanding both will allow you to draw a true comparison between it and more familiar traditional cameras.
2. Lenses – If you are buying a fixed security day/night camera that requires a C or CS mount lens, be sure to get a lens that is rated for use with infrared light. IR ready lenses allow for the proper passage of IR light, the full use of the camera’s day/night capabilities, and of course, lower light performance.
3. S/N Ratio – There are many cameras on the market place with low lux ratings, but this does not always mean they will produce a good picture in low light. To ensure you get both, select a camera with a signal-to-noise ratio of 48dB or higher.

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