Ordinary users often judge HDR performance based on subjective impressions, but professional monitor reviews, calibration, and troubleshooting require quantitative data. Whether brightness meets standards, color gamut coverage is complete, black levels are pure, and local dimming is effective all need to be evaluated using professional HDR testing tools and standardized procedures. This article will introduce the core metrics of the DisplayHDR certification standard, and explain in detail how to use HDR test signals, luminance meters, colorimeters, and software tools to complete a comprehensive evaluation of peak brightness, black depth, color gamut coverage, and local dimming capability.

1. Understanding the DisplayHDR Certification Standard

DisplayHDR is a display HDR performance certification specification introduced by VESA (Video Electronics Standards Association) and is currently the most common HDR grading standard in the consumer market. Understanding its tiering logic is the foundation for conducting professional testing.

  • DisplayHDR 400: Entry-level certification requiring peak brightness of no less than 400 cd/m², global dimming support, and color gamut coverage of approximately 95% sRGB. The actual HDR effect is limited and is often criticized as being "only slightly better than SDR."
  • DisplayHDR 600: Mid-range certification requiring peak brightness of no less than 600 cd/m², local dimming capability, and color gamut coverage of approximately 99% sRGB and 90% DCI-P3. The HDR effect is noticeably improved.
  • DisplayHDR 1000: High-end certification requiring peak brightness of no less than 1000 cd/m², with higher requirements for local dimming, black levels, and color gamut, suitable for users pursuing high dynamic range for gaming and video viewing.
  • DisplayHDR True Black Series: Targeted at self-emissive panels such as OLED, with relatively lower peak brightness requirements (400/500/600), but extremely strict black level requirements (below 0.0005 cd/m²), emphasizing infinite contrast ratio.

During testing, the monitor's measured data can be compared against certification standards to determine whether its actual HDR capability meets the advertised level.

2. Tools Required for Professional HDR Testing

Professional testing requires three types of tools: HDR test signal sources, optical measurement instruments, and analysis software. The following are common configurations:

  • HDR Test Signal Generator: Can be a hardware signal generator (such as Murideo, QuantumData) or software running on a PC (such as MadVR, PotPlayer with test videos, or dedicated HDR test pattern packages). Test signals should include various brightness windows, color gamut patterns, and grayscale transitions to trigger the display's HDR performance.
  • Luminance Meter and Colorimeter: A luminance meter is used to measure absolute brightness, and a colorimeter (such as X-Rite i1Display Pro, Calibrite ColorChecker Display) is used to measure color coordinates. For local dimming testing, high-precision instruments capable of low-luminance measurement are also required.
  • Software Analysis Tools: DisplayCAL (open-source color management software), CalMAN (professional calibration software), HCFR, and others can read colorimeter data and generate reports on brightness, color gamut, and gamma curves. Additionally, the HDR calibration tool built into Windows can serve as an auxiliary tool.
  • Light-Controlled Environment: Professional testing should be conducted in a darkroom or low ambient light environment to prevent ambient light from interfering with measurement results.

3. Core Test Metrics and Test Methods

Professional HDR testing needs to cover four key dimensions: peak brightness, black depth, color gamut coverage, and local dimming capability. The following are the key testing points for each metric:

  • Peak Brightness: Use a 10% window white test signal, set the monitor to HDR mode and maximum brightness. Measure the center luminance of the window with a luminance meter and record the maximum value. Also test brightness at 2%, 5%, 25%, 50%, and 100% window sizes to observe whether brightness roll-off conforms to HDR curve expectations.
  • Black Depth: Display a full black signal and measure the center luminance of the screen with a luminance meter. For LCD monitors, black levels typically range from 0.05 to 0.5 cd/m²; OLED panels may be below 0.001 cd/m². The lower the black level, the higher the contrast ratio and the purer the shadow detail. Note that when local dimming is enabled, a full black screen may significantly reduce brightness due to zone dimming, so testing should be performed with dimming both on and off.
  • Color Gamut Coverage: Display pure red, pure green, pure blue, and various saturation levels of colors, use a colorimeter to measure color coordinates, and calculate sRGB, DCI-P3, and Rec.2020 color gamut coverage and volume. HDR monitors are typically required to cover at least 90% DCI-P3. Higher color gamut coverage results in richer HDR color performance.
  • Local Dimming Capability: Use checkerboard or small window test patterns to observe halo control, brightness leakage, and zone edge transitions between dark and bright areas. Professional testing measures the luminance of black areas surrounding bright blocks to evaluate halo suppression. Good local dimming effectively improves contrast, while poor haloing can severely impact the viewing experience.

4. Complete Professional HDR Testing Workflow

The following is a standard HDR testing workflow suitable for reviews, calibration, or troubleshooting:

  • Step 1: Environment and equipment preparation. Turn off ambient lighting, warm up the monitor for at least 30 minutes, ensure the colorimeter and luminance meter are calibrated, connect the HDR signal source, and confirm display resolution, refresh rate, and color format (RGB Full or YCbCr 4:4:4 recommended).
  • Step 2: Set HDR mode. Enable HDR in system display settings, switch the monitor OSD to HDR mode (or the corresponding certified mode), and disable dynamic contrast, color enhancement, and other post-processing features to avoid interference.
  • Step 3: Peak brightness testing. Use a 10% window white signal, record peak brightness at different window sizes, and plot a brightness-versus-window curve to evaluate highlight impact and sustained brightness stability.
  • Step 4: Black depth and contrast testing. Display a full black signal and ANSI contrast pattern, measure black levels and bright block luminance, and calculate contrast ratio. For monitors with local dimming support, test performance with dimming both on and off.
  • Step 5: Color gamut and grayscale testing. Use a colorimeter to measure the three primary colors and grayscale (from 0% to 100%), and calculate color gamut coverage, color temperature consistency, gamma curve, and Delta E. In HDR mode, the ideal gamma should closely follow the ST.2084 (PQ) curve.
  • Step 6: Local dimming specialized testing. Play test videos with small moving windows, starfields, subtitles, and other content to observe haloing, brightness flickering, and shadow detail retention, record subjective evaluations, and take photos for archival purposes.
  • Step 7: Generate test report. Compare measured data against DisplayHDR standards, summarize the strengths and weaknesses of the monitor's HDR performance, and provide calibration recommendations or usage scenario suggestions.

5. Common Issues and Precautions

  • Color temperature drift in HDR mode: Many monitors exhibit color temperature that is too high or too low in HDR mode. Adjust RGB gain in the OSD or use software-based 3D LUT calibration.
  • ABL (Automatic Brightness Limiter) affecting measurements: Some monitors reduce brightness in full-screen high-brightness scenes to protect the panel. When testing peak brightness, use a small window signal and note the window size.
  • Relationship between local dimming and black levels: Enabling local dimming can significantly lower full-screen black levels but may also introduce haloing. Professional testing should record data for both on and off states to provide a comprehensive evaluation.
  • HDMI cable and interface bandwidth: Older HDMI 2.0 cables may not be able to transmit 4K 120Hz HDR signals. Confirm that the cable specification and interface bandwidth meet requirements before testing.
  • Relationship between online testing and professional testing: Online HDR tests can serve as a quick screening tool to help users determine whether further calibration or repair is needed, but they cannot replace precise measurements from luminance meters and colorimeters. Professional testing should be completed with hardware tools.

6. Summary

The core of professional HDR testing lies in "letting the data speak." By clarifying test objectives through DisplayHDR standards and systematically measuring peak brightness, black depth, color gamut coverage, and local dimming capability with HDR test signals, luminance meters, colorimeters, and software tools, one can accurately evaluate a display's true HDR performance. Whether you are a hardware reviewer, a professional user, or an enthusiast pursuing ultimate picture quality, mastering this testing workflow will help you better understand device performance and make more informed purchasing and usage decisions.