For the benefit of those Risk Xtra readers focused on CCTV as part of their risk and security management remit, Uri Guterman shines a light on Wide Dynamic Range and what benefits it brings to video surveillance systems.
The latest generation of HD cameras has raised end users’ expectations about the quality of images they can expect to capture from their surveillance systems. The superb ‘need to be seen to be believed’ images delivered by some HD cameras, in fact, are now way beyond what could have been imagined even just a few short years ago.
However, the quality of these images can be significantly affected by varying lighting conditions that may exist in a camera’s field of view. Some parts of an image can be very bright, while other sections are extremely dark. This scenario is quite typical in office reception areas, for instance, and along retail store fronts where sunlight shining in through windows differs greatly in its intensity to the internal lighting. The extent of this difference in the lighting levels is described as the dynamic range.
This is why you are more than likely to see Wide Dynamic Range listed among the key features offered by most of today’s surveillance cameras. Wide Dynamic Range is intended to balance out lighting differences. In operation, cameras may use one or other of two ways to achieve this. The first is to take samples of the pixels which make up an image and then use the processing power of a camera’s chipset to automatically make the changes necessary to deliver an image where all areas can be clearly seen.
The second method involves capturing in quick time more than one version of the same image with each at different exposure levels. Almost all cameras able to offer Wide Dynamic Range do so by capturing just one underexposed and one overexposed frame of the same scene. These are then simultaneously processed to produce one optimised image.
Wisenet X 2 megapixel cameras have taken this a stage further. Their advanced form of Wide Dynamic Range uses four frames to create a more natural image at up to 150 dB and at 30 images per second. It also incorporates some innovative technology that removes the blurring which can occur when conventional Wide Dynamic Range is in use. What has made this possible is the massive processing power of the chipset at the heart of the Wisenet X cameras.
While Wide Dynamic Range may only be one of many features listed on a camera’s specification sheet, the contribution it can make to the effectiveness of a video surveillance system should never be underestimated. Indeed, any form of Wide Dynamic Range will deliver some benefit, but if you’re intending to locate cameras in extremely varying lighting conditions, it will always be wise to take a very close look at what the manufacturer claims it can deliver through its product offer.
End users should never hesitate to ask for a demonstration if they have any doubts.
Uri Guterman is Head of Product and Marketing for Hanwha Techwin Europe
*Do you have some questions about Wide Dynamic Range? If so, send an e-mail to Uri Guterman at firstname.lastname@example.org