HellasCams - The Myth of the Low-Lux Camera

The Myth of the Low-Lux Camera

By Jack Gin - President and CEO of Extreme CCTV Inc.

Jack Gin is a regular contributor to various trade publications and speaker at several events in North America and the U.K. on the topics of infrared, night vision surveillance and security.

The myth of low-lux, zero-lux and day-night cameras causes a great deal of confusion and disappointment in the security industry. Security professionals can easily achieve outstanding night vision if they understand active-infrared illumination. The myth of low-lux, zero-lux and day-night cameras causes a great deal of confusion and disappointment in the security industry. Security professionals can easily achieve outstanding night vision if they understand active-infrared illumination.

"I have a low-lux, day-night camera, but the camera cannot see anything at night!" is something that security professionals hear more often than they should. Dark scenes that stay dark even with near-zero-lux cameras. Most cameras have sensitivity ratings as low as 0.05 lux, which is 20 times less than that of typical moonlight. Yet, why do cameras rated at 0.05 lux fail to get great night-time video under moonlight or even under streetlights?

Major camera manufacturers still claim that their day-night cameras obtain video in the dark. Other day-night camera manufacturers claim video performance at zero lux. This suggests that cameras perform in complete darkness, but qualifications to such boasts are likely. If there is no light, there can be no picture. This is a fact of physics.

Additionally, street lighting should not be the answer. Street lighting and other forms of ambient lighting may help make streets brighter but often do little for critical target areas; they can even make matters worse. When end-users demand high-quality video at night, lighting needs to be designed specifically for surveillance, not for streets and not for architectural ambience.

Cameras by themselves cannot see in total darkness. The truth is that day-night cameras cannot pull pictures out of the dark without some form of illumination. For day-night cameras to create great video in the dark, cameras must be IR-sensitive and there must be invisible infrared illumination on scene.

Security professionals can easily achieve outstanding night vision if they understand active-infrared illumination.

Lux
What exactly does lux rating mean? Lux measures light visible to the human eye. Lux meters stay within narrow human-eye bandwidths and, certainly, do not measure active-infrared light, the kind of illumination that enables effective night surveillance. For example, a scene at zero-lux (no visible light) is completely dark to humans. If the same zero-lux scene is then well-illuminated by infrared, it still remains zero-lux and completely dark to humans. But to IR-sensitive cameras, it resembles normal monochrome daytime images.

To present these facts in another way, a day-night camera performs at zero lux only if it as high sensitivity to infrared and there is infrared light on the scene. Low-light and day-night cameras with low-lux ratings almost never provide great night vision by themselves. If a dark scene needs to be under critical surveillance, then infrared illumination is required no matter what the camera lux rating. This is the qualification that is rarely mentioned and often not understood by inexperienced security installers. With the myth of day-night cameras exposed, progressive security providers can learn how to achieve fantastic night vision with active-infrared illumination for clients. The good news is that today's day-night cameras are very sensitive to infrared light and produce stunning video surveillance at great distances when matched with the best infrared illuminators.

Infrared illumination allows day-night cameras to work effectively in the dark, but what exactly is infrared illumination? Active-infrared illumination, for CCTV purposes, is light in the wavelength region of 700 nanometers to 1,000 nanometers that the human eye cannot see; all colors of light visible to the human eye fall within a small area of the electromagnetic spectrum. Radio waves, microwaves and X-rays are all part of the same spectrum; the only difference is wavelength. The problem is that humans cannot see the majority of these wavelengths.

IR-sensitive cameras, however, see what human eyes cannot. Special CCD technology allows sensitivity to light in infrared wavelengths. What is a completely dark scene to humans is a perfectly illuminated image to an IR-sensitive camera if there is sufficient IR light on the scene.

Active IR
In active-infrared night vision, IR-sensitive cameras are only part of the story. The term "active" differentiates active-infrared night vision from other night-vision technologies such as passive-infrared, thermal-imaging and intensified-CCD cameras. Thermal cameras, for example, passively detect temperature differentials such as warm bodies on colder scenes and produce images. Results are generally adequate for detection purposes, but there is a marked decrease in image resolution, typically in the range of 320 x 240 pixels. Low resolution often makes it impossible to distinguish between friend or foe, and images are considered unsatisfactory for high-resolution needs of technical video surveillance.

Active-infrared systems are fundamentally different, producing high-resolution images by actively illuminating scenes. Unlike in the U.K. where terrorism initiated wide use of active-infrared systems over a decade ago, North American CCTV professionals are just beginning to realize the benefits of active-infrared technology.

High-resolution images can be achieved reliably and very cost-effectively. Design and installation become intuitive with practice and are quickly mastered. Top systems integrators regularly install infrared illuminators like Derwent's US Patented UF500 [PDF] for projects that range from general area surveillance to 24/7 video analytics using intelligent software such as VMD (video motion detection). It is now widely understood by specifying security consultants that active-infrared night vision enables high-resolution performance on a 24-7 basis under all lighting conditions.

Conclusion
Because of the growing need for night vision surveillance, security consultants are also specifying Integrated Day-Night cameras which combine IR-sensitive CCDs and infrared illumination in a single housing. These cameras, which include the US Patented EX36 [PDF] for prison use and the patent pending EX82 [PDF] for high-end surveillance, provide a single "Plug and Play" solution guaranteed to deliver outstanding pictures at day and at night. These products are two examples of how easy it is for security professionals to deliver outstanding night-time performance to their clients who are now expecting 24/7 security.

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