Many of us may hear about the term “WDR” in photography. So, what is WDR camera? A brief explanation: When a camera capture a image, it merges the bright (or overexposed)areas and dark areas into each other – In this way, the bright areas get slight darker, and the dark areas get brighter, and the image becomes more natually presented. The key technology to achieve this is WDR (wide dynamic range). WDR technology can simultaneously adjust the light and dark areas of the image to achieve an overall light balance, contributing richer details with images. In this article, we’ll dive into this interesting technology in length.

WDR function comparison

1. What is WDR

WDR stands for Wide Dynamic Range. By using different shutter speeds, a WDR camera captures images of bright and dark areas (where a fast shutter speed captures less light and a slow shutter speed captures more light) and then combine them into a single image. In other words as mentioned in the preface, dark areas are brighter, and bright places are darker. In this way, the image output by the camera is overall clearer.

2. How Does WDR Technology Work?

The most important thing in realizing WDR technology is the use of camera shutter speed (or exposure time). With WDR technology, a WDR camera uses different shutter speeds to control the sensor to receive different amounts of light to achieve a balance of light and dark in the image.

Specifically said:

In dark areas, the cameras use long exposure times (slow shutter speeds) to expose the light-sensitive sensor to light for a longer time and capture more light to compensate for dark area images.

In the bright area, the camera uses a short exposure time (fast shutter speed) to allow the sensor to be exposed to light for a short time and capture less light to output the bright area image.

Finally, the two obtained images are combined by the processor to output a light-balanced image.

WDR cameras are suitable for areas with obvious light differences and high-quality surveillance requirements such as the entrances and exits of underground parking lots. WDR can balance the strong sunlight at the exit and the backlight shadows inside the parking lot.

 

3. Differences Between True and “False” WDR

3.1  WDR vs dWDR

There are two types of wide dynamic range, namely digital WDR(dWDR) and true WDR. Both are designed to deal with the presence of bright and dark areas in the same frame, solving the challenge of cameras balancing differences in brightness. However, there are differences between the two technologies. Digital WDR surveillance cameras use image sensors and mainly rely on digital signal processors (DSP) to adjust the image brightness range. That is to lighten dark areas and darken overly bright areas. The true WDR uses two sensors (CCD/CMOS) with different exposures to capture bright areas and dark areas respectively, and then merges them through technology to generate an image with balanced lighting.

In general, true WDR is more mature than dWDR in processing the difference between light and dark images and details. Under the same conditions, compared to dWDR, WDR can present a better image.

3.2 WDR vs BLC

BLC is the abbreviation of “Backlight Compensation”, which means backlight compensation. Designed to compensate for image problems in backlight conditions by automatically adjusting exposure. When there is strong light behind the subject (such as sunlight), traditional exposure settings may cause the foreground object to be too dark and the backlight area to be too bright. BLC technology improves image quality by adjusting exposure so that foreground objects are clearly visible.

BLC technology makes the overall image brighter. Although dark areas are brightened and visible, this also leads to overexposure of bright areas and image distortion. WDR balances this light difference very well. It reduces the over-illumination of bright areas while brightening dark areas, thereby outputting a well-illuminated image.

When using a single technology, WDR handles image light contrast issues better than BLC. The greatest effect can be achieved when the two are combined. WDR focuses on the overall image brightness difference, and BLC focuses on the brightness of foreground objects under backlight. BLC adjusts the exposure to ensure that foreground objects are still clearly visible under backlight conditions. On this basis, WDR further processes the brightness range of the entire picture to ensure that details are displayed in a balanced manner in each area. WDR and BLC used together can help reduce or avoid overexposure and shadow problems. WDR’s optimization of the overall dynamic range, combined with BLC’s foreground adjustment, helps produce more natural, higher-quality images.

When using a single technology, WDR handles image light contrast issues better than BLC. The greatest effect can be achieved when the two are combined. WDR focuses on the overall image brightness difference, and BLC focuses on the brightness of foreground objects under backlight. BLC adjusts the exposure to ensure that foreground objects are still clearly visible under backlight conditions. On this basis, WDR further processes the brightness range of the entire picture to ensure that details are displayed in a balanced manner in each area.

WDR and BLC used together can help reduce or avoid overexposure and shadow problems. WDR’s optimization of the overall dynamic range, combined with BLC’s foreground adjustment, helps produce more natural, higher-quality images.

3.3 WDR Camera Vs Standard Camera

WDR technology helps ensure the camera captures all details clearly in high-contrast scenes. WDR means on camera is a master of image processing technology. Standard cameras may have difficulty maintaining a balance between light and dark areas when faced with high-contrast scenes. Such as overexposure or loss of detail.

Items WDR camera Standard camera
High Contrast Captures both strong light and shadows, handling high-contrast scenes May lose details between strong light and shadows
Light Adaptability Performs well in varying lighting conditions, exhibiting strong adaptability Sensitive to changes in lighting, may face exposure issues
Low-Light Imaging Improves performance in low-light conditions, providing clearer night images May struggle in low-light, resulting in blurry or noisy images
Face Recognition Detail Capture Aids in face recognition and captures details in scenes Limited performance in complex lighting conditions
Exposure Balance Achieves balanced exposure across the entire scene through intelligent exposure control Relies on fixed exposure, challenging in varying lighting conditions

4. How to choose a WDR camera

The effect of WDR usage is usually measured in dB. The higher the dB value, the better WDR can handle changes in lighting conditions, ensuring that both light and dark parts of the image are fully displayed. Under the same conditions, a 120dB WDR camera is a better choice.

WDR120VS140

WDR Camera Exmaple:

① Hikvision WDR Camera:DS-2CD2T66G2-ISU/SL

Core specifications:

  • 6 MP Resolution
  • DarkFighter technology
  •  120 dB true WDR technology
  • Efficient H.265+ compression technology
  • Focus on human and vehicle targets classification based on deep learning
  • Active strobe light and audio alarm to warn intruders off
  • Provides built-in two-way audio
  • IP67 water and dust resistant 

②Dahua WDR camera: DH-IPC-HDBW2831R-ZS

Core specifications:

  • 8MP resolution
  • WDR, 3D NR, HLC, BLC, digital watermarking, applicable to various monitoring scenes
  • supports 2688×1520 (2688 × 1520) @25/30 fps
  • SMART H.264+/H.265+ decoding
  • Built-in IR LED, max IR distance: 40 m
  •  Intelligent detection: Intrusion, tripwire

  • Abnormality detection: Motion detection, video tampering, no SD card, SD card full

  • Supports max. 256 GB Micro SD card

  • PoE power supply/ DC12V

  • IP67, IK10 protection

Conclusion

The birth of various image technologies such as WDR has added significant power to cameras to output clear and detailed images under various complex light conditions. Therefore, it is necessary to consider the differences between these technologies when choosing the right surveillance camera for your needs. Of course, if you can avoid complex lighting such as strong light and backlight, please give priority to extending the lifespan of the camera.

 

If you need more assistance to make the right choices for security cameras,  be free to reach us:

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