Uri Guterman, Head of Product & Marketing for Hanwha Techwin Europe, explains how recent advances in Wide Dynamic Range technology are making a significant contribution to the effectiveness of video surveillance systems.
The superb ‘need to be seen, to be believed’ images delivered by the latest generation of IP network video surveillance HD cameras are now way beyond what could have been imagined just a few 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 and retail storefronts 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.
The greater the level of dynamic range, the greater the challenge in terms of a camera capturing images which include a clear view of both the inside of a building and the people entering it. With WDR not in use, an image made up of under and overexposed areas might make a shop floor wrongly appear to be in the dark or the view of the entrance might be too bright to enable the capture of usable images of anyone coming through it.
This is why you will see Wide Dynamic Range (WDR) listed among the features offered by almost all of today’s professional-level video surveillance cameras. WDR is intended to balance out lighting differences, with cameras from different manufacturers using several ways to achieve this. The first is to take samples of the pixels which make up an image and then use mathematical algorithms to ‘calculate’ what the colour across all areas of the image should be.
The second and more accurate method involves capturing in quick time more than one version of the same image with each at different exposure levels. Almost all cameras which are able to offer WDR do so by capturing just one underexposed and one overexposed frame of the same scene and these are simultaneously processed to produce one optimised image.
An advanced form of WDR incorporated into Wisenet X 2 megapixel cameras has taken this second method a stage further. It uses 4 frames to create a more natural image at up to 150dB and at 30 images per second. It also incorporates some innovative technology that removes the blurring which can occur when conventional WDR is in use. What has made this possible is the massive processing power of the chipset which is at the heart of the Wisenet X camera models.
WDR has perhaps been taken to its ultimate level with the recent introduction of Hanwha Techwin’s proprietary Wisenet7 chipset. This is equipped with extremeWDR, Hanwha Techwin’s latest multi-frame WDR technology, which lets you take full advantage of image contrast to see detailed objects even in environments with strong backlight conditions. extremeWDR utilises a number of new technologies, including Local Contrast Enhancement which ‘stretches’ the contrast of any image by analyzing neighbouring pixel data and Scene Analysis which manages the dynamic range and refines the overall tone of an image.
Whilst WDR 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 not be underestimated. Indeed, any form of WDR will deliver some benefit, but if you are intending to locate cameras in varying lighting conditions, it will always be wise to take a very close look at what the manufacturer claims it can deliver. Never hesitate to ask for a demonstration if you have any doubts.
Do you have some questions about WDR? Email Uri Guterman at [email protected]