Wide Dynamic Camera

 CCTV SECURITY SYSTEM NEWS – Wide Dynamic Camera

A wide dynamic camera conjures images of an incredibly large (In a horizontal direction) camera, somewhat like an oversized wide-angle lens. However, that’s not what a wide dynamic camera is at all. In fact, some ultra-small hidden covert cameras are also wide dynamic cameras. So just exactly what is the wide dynamic range of a camera? Read on to find out.

A wide dynamic camera is actually a camera with a highly specialized function to assist the image capture process. When cameras possess the circuitry to support this function we say that they have Wide Dynamic Range or WDR.

The whole idea behind this business of a wide dynamic camera is to produce a superior image, at least superior when compared to the image from an exact same camera that does not support WDR. WDR helps to provide clear video images under unbalanced, poor lighting conditions: Specifically, when the intensity of the light varies such that that there are incredibly bright and dark areas that appear simultaneously in the field of view (which is destined to become the video image) of the camera.

Overly dark areas and overly saturated light areas, especially over saturation of back lighting is the problem that the wide dynamic camera is trying to solve. The better the WDR of a camera the better video image produced under undesirable backlighting conditions and other over contrast conditions.

Specifically, a wide dynamic camera filters the intensely bright back light that may surround an object therefore enhancing the ability to distinguish features and shapes on the subject that were “washed” out by the intense bright light. The dynamic range of a camera is normally defined as the ratio of the brightest point of an image to the darkest point of the same image. Some also refer to this situation as “maximum contrast.”

In essence, what happens in this situation is the intensely bright (back) light is causing the camera to adjust itself to that particular condition. When this happens, the video image produced is a washed out image near the light source and everything else being to dark to recognize. This does not necessarily apply to images with steady light sources; it can occur when momentary intense light appears (for what ever reason) throwing the entire camera off balance.

Perhaps one of the best examples of a problem wide dynamic range is when a camera attempts to capture an image in front of a large storefront window. The object inside the store appears far too dark with the sunlight pouring through the front window and washing out the details of most of the field of view of the camera.

There are several different approaches to the solution of this problem and although each method’s goal is the same result (a balanced, detailed video image) the process they use to go about correcting the situation may be different. Basically there are two major methods or technical solutions that are used to correct the problem and there are additional methods that “hybridize” the process by combing the two basic methods.

The first solution is “multi-frame imaging.” Here the wide dynamic camera captures more than one frame of the field of view. Each of these frames possess their own dynamic range and the camera combines the different frames to produce one WDR image or frame.

The second solution is the use of non-linear sensors (generally logarithmic sensors) where the sensitivity level of the sensor at different light intensities also varies providing the capture of the field of view in one wide dynamic camera frame.

Combinations of the two methods just mentioned are also used. For example, they may include parallel capturing by more than one sensor using a common optical path. Here each sensor captures different levels of the dynamic range of the scene by either different exposures, different optical attenuation in the final optical path, or different sensor sensitivity. There are many more combination methods that may be used as well.

The key is that if you intend to use a camera that will be capturing areas of extremely high contrast or that are back lit by an extremely bright light, you’ll want a good wide dynamic camera to capture the image.