IP Cameras at Low Light

The past 12 months have seen some advancements in technology propel the IP Camera forward as a more useful tool in low-light situations

IP Cameras at Low Light | What Has Changed and How to Choose

Original Article by  Steve Carney posted on Tue, May 01, 2012

IP Cameras at Low Light | What Has Changed and How to Choose

Whether or not it’s deserved, IP cameras have developed a reputation for poor performance in low light. And because low-light conditions exist with nearly all camera installations, this perception has inhibited some organizations from adopting the technology, in spite of its many strategic and far-reaching benefits.

The challenges have had less to do with delivering the video over an IP network than with the CMOS sensors that most IP cameras use. Historically these sensors have been able to deliver higher megapixel resolution, but they weren’t able to match the CCD sensors often used in analog cameras for low-light performance. Because of this, some IP cameras generate grainy images at low light, resulting not only in decreased picture clarity but also in higher bandwidth usage and increased storage, since compression techniques interpreted the graininess as motion in the scene.

The past 12 months, however, have seen some advancements in technology propel the IP camera forward as a more useful tool in low-light situations. Camera manufacturers have been able to leverage advances in sensors, encoding and processing power born from the automotive and other industries to resolve many of these issues. And High Profile H.264 compression helps to more effectively manage bandwidth usage, while more sensitive elements in the sensors provide higher-quality images.

Companies hoping to benefit from these advances should look for the following features in low-light IP cameras:

1) True day-night function, or an IR cut-filter. This means that when light drops below a certain level, only black and white is getting into the sensor, increasing its sensitivity.  This improves image clarity while decreasing noise or graininess in the image, which can be interpreted as motion in the encoder.  When the encoder compresses an image with a higher level of motion or noise, the bandwidth consumption can skyrocket.

2) An IR-corrected lens. Infrared light is invisible to the human eye, but it’s not invisible to camera sensors. It also travels at different wavelengths from visible light.  These differences result in the focal point that varies between the lights sources and means the sensor must actually move to achieve focus when lights sources produce varying amounts of IR light. If there is a lot of IR light in a scene that a camera has to adjust to, it can change the focal point of the camera. For instance, halogen light is very IR heavy when compared to fluorescent light, which has almost no IR light.  If you have a halogen light in an office and you turn that light off, the camera can go out of focus because it was focused for that light source. IR-corrected lenses resolve this problem.

Historically, “auto-back focus” was used to compensate for this type of change.  However, given that auto-back focus can hunt for a focal point for quite some time, often ending up at the wrong one, it is less effective in serving customers that expect 100% uptime in their security system.

3) A High Profile H.264 compression. There are multiple profiles of H.264 and users should be wary of which profile a manufacturer uses.  High profile is generally more processor intensive and is a bit harder for a manufacturer to deliver well.  But the result is worth the development effort.

Buyers should beware of the “base profile” H.264 implementations.  While the high profile is used for media such as Blu-ray, base profile is used for applications like teleconferencing.  The image quality standards between those two uses speak for themselves.

4) For applications at the very bottom of the low-light range, look for a camera that supplies its own IR illumination. Watch this quick video about the added benefits of IR illumination.

We encourage everyone who is concerned about low-light performance to enlist the help of their systems integrator in lining up their camera options where they’re intended to be used and test them out against each other.

Whenever possible, camera shoot-outs should be the norm for customers who care about image quality in any conditions, and this is especially true for low light applications.  At the end of the day, this is the best way to ensure that the best technology will be chosen for the application.

 

 

  • by CSS
  • posted at 5:01 pm
  • May 1, 2012

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