Color Grading: Calibration Guidelines
SDR Reference Monitor (Minimum Requirements):
- Color Gamut: Rec.709
- White Point: D65
- EOTF: BT.1886 (Gamma 2.4)
- Black Level: 0.05 Nits or lower
- Peak Luminance: 100 nits
- Measured Contrast Ratio: 2000:1
HDR (Dolby Vision) Reference Monitor (Minimum Requirements):
- Color Gamut: P3
- White Point: D65
- EOTF: SMPTE 2084 (PQ)
- Black Level: 0.005 Nits
- Peak Luminance: 1000 Nits
- Measured Contrast Ratio: 200,000:1
For detailed information on color grading systems and monitors used in Dolby Vision mastering, please see the Dolby Vision Best Practices and Monitor Requirements.
Critical Viewing Environment
The Color Grading critical viewing environment should first consist of a calibrated UHD display, treatment of lightning and room decor, as well as the appropriate placement of the observer relative to the screen.
- Surround Illumination: the area around the screen should be lit from a light source and reflective surface whose color temperature matches that of the display i.e. D65 for both SDR and HDR viewing. All wall treatments should be of neutral matte material with no distracting images or patterns.
- Surround light level: 5 nits
- Surround extent: at least 90 degrees horizontal field-of-view (FOV) and at least 60 degrees vertical FOV from observer.
- Viewing distance: Ideal observer viewing distance is 3 - 3.2 picture heights for HD and 1.5 - 1.6 picture heights for UHD.
See SMPTE ST.2080-3 for more specific viewing environment requirements.
Calibration Best Practices
Calibration procedures vary between facilities, software, and hardware configurations, but they should all share the same goal of producing standard color space targets, as noted above. The following are some best practices for facilities looking to calibrate a monitor before making color judgements or decisions.
- Setting Black Level
- Use a PLUGE pattern to set black level
- Use Contrast pattern (near-white) to ensure no clipping is occurring as the signal approaches reference white video level.
- Use backlight or contrast control to adjust reference white to desired luminance target (i.e. 100 cd/m2 for SDR)
- Measure at least 11 steps (0-100% at 10% increments)
- Adjust using RGB gain and/or RGB bias to achieve desired white point and luminance at each greyscale level.
- After adjusting gain/bias, repeat #1 and #2
- Adjust as needed to hit target color primaries
Please Note: CalMan software, by SpectraCal, includes a “Netflix Video Monitor” workflow template which offers a step-by-step guide for going through an SDR calibration. The first step of this workflow is to define your desired targets, which should correspond to the standards referenced above.
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