HLG Reference EOTF Calculator
Calculate the rendered luminance of an achromatic HLG signal for a nominal HLG display peak and viewing surround.
Results
| Evaluated HLG Signal | |
|---|---|
| Surround Luminance (LS) | |
| Black Level Lift (β) | |
| Peak LW Adjusted Gamma (Base) | |
| Surround Gamma Factor (EBU R 167) | |
| Effective System Gamma | |
| Luminance at 109.018% HLG Signal | |
| HDR Reference White Luminance (75% HLG) |
Display
Enter the measured achromatic luminance produced by a nominal 100% HLG signal in the exact display mode and window size being modeled.
Do not substitute an advertised HDR peak, EDID/CTA maximum, Windows HDR Calibration maximum, or PQ review measurement unless it has been verified to equal the display's nominal 100% HLG output.
For EBU R 167 extended modes such as "1000ext", enter the nominal Lw (1000), not the brighter 109% output.
Viewing Environment
Typical Values (ITU-R BT.2408-9 Table 5):
- Office (Sunny Day): 130 Lux
- Office (Cloudy Day): 75 Lux
- Edit Suite: 50 Lux
- Grading Suite: 25 Lux
- Prod. Gallery/Dark Grading: 3 Lux
(Perpendicular to the monitor surface)
Common Reflectivity Estimates:
- Fresh Matte White Wall: ~0.8 to 0.9
- Light Grey / Off-White Wall: ~0.6 to 0.7
- ITU-R BT.2408-9 Table 5 assumes approximately 0.6 for light-coloured walls.
- This estimate uses Ls = illuminance × reflectivity / π and assumes a diffuse Lambertian surround.
- 18% Grey Card: 0.18
- Darker surfaces have lower values.
Typical Values (ITU-R BT.2408-9 Table 5):
- Office (Sunny Day): 25 cd/m²
- Office (Cloudy Day): 15 cd/m²
- Edit Suite: 10 cd/m²
- Grading Suite: 5 cd/m²
- Prod. Gallery/Dark Grading: 0.5 cd/m²
Advanced Settings
ITU-R BT.2408-9 identifies 75% HLG as the nominal HDR Reference White signal.
A custom value is evaluated as an arbitrary HLG signal level; it is not automatically a new paper-white recommendation. The reference default is 75%.
The accepted limits are the EBU R 103 10-bit total video range, normalized against narrow-range black (code 64) and nominal white (code 940): −6.849315% (code 4) to 109.018265% (code 1019). Negative sub-black values are retained through the BT.2100 black-lift stage for PLUGE evaluation.
Enter the measured minimum visible display luminance in the viewing conditions being modeled.
BT.2100 references PLUGE alignment for determining LB. A value of 0 uses the idealized reference calculation with no black-level lift and is the reference default.
The published low-light β expression reproduces LB only while β ≤ 0.5. The calculator rejects larger black levels instead of silently applying the wrong inverse-OETF branch.
Calculates and displays the luminance produced by the 109.018% HLG total-range maximum, based on the current LW (for 100% signal) and system gamma.
This utilizes the "super-white" headroom defined in EBU R 103.
The value conventionally called 109% is exactly (1019−64)/(940−64) for 10-bit narrow range.
ITU-R BT.2100-3 Note 5f specifies a piecewise function for System Gamma based on Display Peak Luminance: one formula for the 400-2000 cd/m² range and an 'extended' formula for values outside this range.
Enabling this option forces the continuous 'extended' formula (γ = 1.2 × κ^(log2(Lw/1000))) across all peak luminance values. Strict mode follows the published range selection; because the two formulas are not exactly equal, small jumps at 400 and 2000 cd/m² are expected. The forced extended mode avoids those jumps but deviates from the strict range recommendation.
