Camera specifications often list support for 120dB wide dynamic range. Here, 120dB represents a ratio, meaning the camera can capture scenes where the illuminance ratio between the brightest area and the darkest area reaches 1,000,000:1, namely \(10^6:1\).

Why does \(10^6:1\) correspond to 120dB? This follows the defined formula for wide dynamic range ratio: \(\text{dB} = 20\log\left(\frac{\text{Illuminance of brightest area [lx]}}{\text{Illuminance of darkest area [lx]}}\right)\) \(20\log(1,000,000/1)=20\times6=120\text{dB}\)

Essentially, dB is a dimensionless ratio, a pure logarithmic notation without physical units. It carries different practical definitions across various fields, such as sound volume and signal strength. The advantage of the dB scale is it concisely expresses extremely large or extremely small numbers with numerous leading or trailing zeros. For instance, describing dynamic range as 120dB is far more intuitive and compact than writing 1,000,000:1.

Note the different calculation formulas across industries: For power parameters: \(\text{dB}=10\log()\) For voltage or current parameters: \(\text{dB}=20\log()\)

In the security industry, 120dB is a meaningful benchmark, as the human eye can perceive roughly 120dB of dynamic range. This means a 120dB WDR camera delivers dynamic range performance comparable to human vision.

Application Scenarios of Wide Dynamic Range Cameras

Wide dynamic range remains a critical feature for security surveillance cameras, and it is essential for many special industries and scenarios. For example, miniature cameras installed inside bank ATMs facing outward from indoors to outdoors face extreme contrast between bright exterior light and dim indoor surroundings. Ordinary cameras struggle to capture clear facial details, so WDR-enabled cameras are mandatory. Similarly, cameras deployed in hotel lobbies monitoring entrance corridors looking outdoors require wide dynamic range to clearly identify visitors and their facial features.

Typical applicable scenarios:

• Entrances with bright outdoor sunlight and dim indoor environments
• Parking lots or tunnels with low indoor illumination against sunlit exteriors
• Outdoor scenes featuring direct sunlight alongside deep dark shadows
• Office buildings or shopping malls with heavy light reflection through extensive windows

Alternative Terminology

Wide Dynamic Range, abbreviated as WDR. Since security image sensors transitioned to CMOS technology, wide dynamic range is also widely referred to as HDR (High-Dynamic Range). The term HDR is standard in film & television, display panels, smartphone screens and professional videography. The security industry adopting the HDR nomenclature aligns it with these adjacent sectors.

Sony, a pioneer in security sensor development, uses additional naming variants for the same function: DOL-HDR or DOL-WDR.

Difference from Backlight Compensation (BLC)

Backlight Compensation (BLC) addresses the issue where surveillance subjects appear underexposed due to an overly bright background. When BLC is enabled, foreground targets become visible, yet originally bright areas will suffer overexposure.

Wide Dynamic Range (WDR) enables balanced clarity across the entire frame, eliminating both overexposed zones and heavily shadowed, underexposed regions.