| Wide Dynamic Range (WDR) |
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| November 2010 | |
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WDR is an image processing technique. It enables image details to be displayed at all light levels. In a typical 24 hour day, various conditions exist such as reflections, glare, car headlights, and direct sunlight etc and they will make image display difficult. WDR addresses this issue. Not all cameras have WDR capability. Assume a camera does not have WDR unless its spec states so. The next 2 paragraphs briefly explained the issue and indicate the resolution approach. The information came from IE Times. (1) Dynamic range is the ratio of the brightest image that can be captured by the imaging system to the darkest image that can be captured. Light intensity greater than the brightest possible image will cause the sensor to saturate, while light intensity less than the darkest possible image will not register on the sensor. Both of these conditions distort the image, hiding potentially vital information that lies outside the dynamic range of the sensor. (2) When an exposure begins, each pixel is charged at a rate that is proportional to the intensity of the light that strikes it. A stronger light source will charge a pixel more quickly than a weaker light source. Existing analog technology typically uses a single exposure time for all pixels. At the end of the exposure, the camera will sense the total charge accumulated in each pixel. But that means some pixels (the brighter ones) may be overexposed while others (the darker ones) may be underexposed. |