3 Things You Need to Know About WDR on KBVISION Cameras

Vũ Khôi

Author at Wotech Electronics Blog

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You need to install a camera at an entrance area. The problem: light shining back into the camera at that spot washes out the image, making it hard to capture who is coming and going. The solution is a security camera with good "Wide Dynamic Range" (WDR) — an answer to this common contrast problem.

Here are the 3 things to know about WDR:

What does WDR do?

Dynamic range refers to the ratio between the largest and smallest measurable values of something. In the case of a surveillance camera, dynamic range measures the ratio between the brightest and darkest elements of an image. WDR technology excels in high-contrast scenes, balancing the bright and dark areas simultaneously so the image isn't washed out or too dark. Put simply, WDR technology helps a camera handle backlighting better.

Decibels (dB) are the unit in which dynamic range is measured. The higher the dB ratio, the better the camera's backlight handling — which translates into a sharp, true-to-life image.

How WDR works

Security cameras with WDR technology use either digital WDR (DWDR) or True WDR. True WDR uses the image sensor and a digital signal processor (DSP) to deliver even lighting across all areas of the image. A surveillance camera with true WDR has two sensors that perform two scans of each video frame. The first scan runs at a slow speed (to gather more light), showing the image under normal lighting. The second scan runs at a high speed to gather less light and capture the image's brightly lit background. The DSP combines the two scans into a single, balanced, well-illuminated image.

DWDR uses an algorithm instead of the sensor to digitally brighten the overly dark areas and tone down the overly bright ones. DWDR relies on the DSP chip rather than the image sensor to provide WDR. It adjusts each individual pixel of the image and calculates the exposure accordingly. This technique has some limitations; heavy manipulation of pixels makes the overall image grainier. On the other hand, DWDR doesn't need an expensive image sensor, so DWDR can be a more economical choice when WDR is required.

When you don't have WDR

There are two options for improving image exposure without WDR. In a high-contrast, backlit scene, the camera will adjust to the average illumination level, which darkens the image. Without WDR, backlight compensation (BLC) brightens the image so you can see the dark details better. BLC is a legacy technique that uses the DSP to raise the exposure level for the entire image. Rather than balancing brightness across the overexposed and underexposed areas of the image the way WDR does, it brightens the whole image. It's a good solution for preventing completely washed-out images that are too bright.

Highlight compensation (HLC) is a technology in which the image sensors detect strong light in the image and reduce exposure in those areas to improve overall image quality. In a dark scene with glare from hotspots (for example, headlights or streetlights), the overall image can become too dark. Without WDR, use HLC. The camera automatically suppresses the strong light sources, allowing proper exposure of the surrounding areas.

Some models feature true WDR (120dB), BLC, and HLC