Difference between HDR and WDR

Suppose you've ever attempted to record dash cam footage in a scenario with strongly contrasting lighting, for example, during sunrise or sunset where the sun is low on the horizon, causing strong backlighting, shadows, and extreme differences in brightness between the light sky and darker road. 

In that case, and because of the bright sunlight in the background, your footage will result in either of these two outcomes:

Overexposed in the lighter parts of the scene.
Underexposed in the darkened sections, blacking out important details.  
This is because cameras may have a restricted dynamic range in contrast to the human eye, which can adapt to a wide range of lighting situations.

But with Wide Dynamic Range (WDR) and High Dynamic Range (HDR), you can avoid this annoying moment in exchange for clear, crisp, and well-balanced videos.

What is the Dynamic Range?

The dynamic range is the span of light intensities a camera's sensor can capture in a single shot, encompassing the darkest shadows to the brightest highlights while retaining all the intricate visual nuances.

Suppose a dash cam surpasses its dynamic range capacity, it will lead to areas of the recording that are overexposed or underexposed, resulting in a loss of detail in those regions.

Dash cams’ image sensors such as Sony STARVIS can adjust the length of time to take in light (exposure time) to output images, optimized according to the scene's brightness. A short exposure time in a bright environment avoids oversaturation of the photodiode and a long exposure time in a dark environment ensures the collection of a sufficient amount of light.

A non-premium dash camera will have a small dynamic range, either offering very bright and exposed videos, or very dark and underexposed, many even without the ability to automatically adjust as needed. Since this range is very small, it can only provide one or the other, and not both simultaneously. Due to the small dynamic range, the brightest and darkest points of the dynamic range are therefore linked together.

What is Wide Dynamic Range (WDR)?

Wide Dynamic Range (WDR) refers to the camera's ability to catch information in both bright and dark portions of the footage. It creates a final image with balanced brightness and contrast by merging many exposures of the same scene. This is especially beneficial while driving through locations with a lot of shadows, such as underpasses or tunnels, because it allows the camera to catch both dark and light areas at the same time.

To give even illumination to all portions of a picture, WDR employs image sensors and a digital signal processor (DSP). A WDR-enabled camera contains two sensors that scan each video frame twice. The first, shot at a slow shutter speed (to capture more light), depicts the image in normal lighting circumstances. The second scan is performed at high speed to capture less light overall while obtaining a picture with bright light in the background. The camera combines the two scans to create a single, well-illuminated, balanced image.

What is High Dynamic Range (HDR)?

Have you ever had an encounter where the headlight beams of oncoming cars are too bright at night, and you can't open your eyes? Or the license plate of the car in front of you is reflective, and you can't recognize the numbers as your bright headlights shine on? In this type of high-contrast light and dark environment, it is difficult to see clearly. If there is a dispute resulting from a traffic incident, and the footage from a dash camera is unclear and unreadable, it is much less useful. To address this issue, HDR technology has been steadily introduced into dash cameras.

Properly illuminating a highly contrasted image is possible with a dash camera that uses High Dynamic Range, or HDR. 

HDR increases a camera's dynamic range by recording multiple images - one with a short exposure and one with a long exposure - and blending them in real time into one image with the best lighting balance possible.

Is every camera with HDR and WDR the same?

WDR is purely a software solution, whereas HDR is a hardware solution that the image sensor and the main processor must support.

Another thing to consider is the dB units. The dB(decibels) unit is the ratio of the brightest and darkest objects that the camera can catch. This specifies the range across which WDR and HDR operate. The higher the ratio, the bigger the difference between the low-light and high-light spectrums that the security camera can collect, and the better your low-light image will be. In other words, the greater the dB number, the better the camera performs in low and high light. Still, there can only be one victor between the two.

Which is better? HDR or WDR?

WDR and HDR are both capable features in dash cams that are intended to increase the quality of video recordings, especially in low-light situations. While the definition of WDR varies by manufacturer, it generally refers to a camera's ability to generate high-quality photographs in various lighting conditions.

Although WDR can help improve image quality in dynamic lighting circumstances, an HDR camera can better illuminate darker sections of a scene without overexposing lighter areas. It also does not generate noise or affect image quality, which can occur with some WDR cameras.

Which is better for a dashcam truly depends on the camera and the settings under which it will be used. In general, WDR may be more effective for driving in high-contrast areas, but HDR will be better for capturing a wider variety of features and colors throughout the scene.

Our vote goes to HDR, especially for Dash Cams, with newer Dash Cams with top-tier image sensors making the most of this feature.

Beyond Dynamic Range

When choosing a dash cam, the technology behind the camera can also make a huge difference in the quality of the footage you capture.

Considered the most advanced image sensor to date, Sony STARVIS 2 technology improves the detail and clarity in the footage, allowing for more detail in each frame. 

The Sony STARVIS 2 IMX678 image sensor, presented in the VIOFO A229 PRO features advanced noise reduction technology and supports an on-chip lens (OCL) and phase detection autofocus (PDAF) for better focus performance. The Sony STARVIS 2 image sensor also supports DOL HDR and Clear HDR. 

PDAF (phase detection autofocus) is a high-speed automatic focus technology. PDAF typically uses some of the pixels for imaging on the image sensor as pixels for phase detection. 

When the digital-overlap (DOL) HDR feature is on, the image sensor captures two images in succession: one with a short exposure according to the bright region and the other with a long exposure adjusted to the dark region. HDR is realized by synthesizing these two images to complement one another. However, this method involves a slight time lapse between the two shots and this can cause some artifacts, such as a blurred outline and chromatic aberration if the target is in fast motion.

When the Clear HDR feature is on, the image sensor captures two images simultaneously, one with a low gain level set to the bright region and the other with a high gain level adjusted to the dark region. This method has the advantage of delivering images of a moving target without chromatic aberration and other artifacts because the two images are captured at the same time.