HDR→sRGB Tonemapping Workflow 2025 — Reliable Distribution Pipeline

TL;DR

• Goal is "pleasant whites"—smooth highlights take priority
• 10bit→8bit requires debanding + dithering combination
• P3→sRGB demands strict saturation checks for skin/sky/greens

Internal links: P3→sRGB Color Consistency Practical Guide 2025, P3 Images Delivery Guide 2025 — sRGB Fallback and Device Testing Procedures

Production Workflow

1. Source identification (HDR10/PQ/HLG, P3/Rec.2020)
2. Tonemapping and gamma/expansion-compression settings
3. Safe 8bit sRGB conversion (banding prevention)
4. Soft proofing/monitoring verification

Quality Validation

• No artifacts in skin tones/sky/greens
• Consistent ICC profile handling

Common Pitfalls and Solutions

1. Simultaneous highlight clipping and saturation loss

• Symptom: Highlights crush while overall saturation drops
• Solution: Gentle shoulder compression in tone curve, saturation recovery in LCh space

2. 10bit→8bit banding

• Symptom: Contour-line artifacts in gradients
• Solution: Blue noise dithering + light debanding (3x3)

3. P3→sRGB skin tone oversaturation

• Symptom: Skin and red fabrics appear oversaturated
• Solution: Soft proof before conversion, localized HSL saturation reduction

Automation Pipeline (Example)

1. Metadata reading (PQ/HLG, gamut) → conversion preset selection
2. Highlight map generation → rolloff application
3. 10bit→8bit only: inject dithering/debanding
4. P3→sRGB: gentle saturation reduction with skin detection mask
5. QA: chart validation (skin, sky, greens) + threshold checks + visual sampling

Pre-Release Checklist

• [ ] White point and midtone consistency (ΔE2000 < 2 target)
• [ ] Highlight smoothness (visual evaluation + noise metrics)
• [ ] Unified profile embedding and stripping policy

Summary

Highlight handling and 8bit conversion determine quality outcomes. Stabilize initial values through automation, then QA with skin/sky/green validation to prevent artifacts at minimum cost.

Implementation Recipe (Pseudocode)

type ColorSpace = 'P3' | 'BT2020' | 'sRGB';
type Transfer = 'PQ' | 'HLG' | 'sRGB';

interface SourceMeta { cs: ColorSpace; tf: Transfer; bitDepth: 10 | 8 }

function tonemap(src: Buffer, meta: SourceMeta) {
  // 1) Inverse OETF/OOTF to linear space
  // 2) Generate highlight map, apply rolloff (shoulder)
  // 3) P3/BT.2020 → sRGB gamut mapping (skin priority)
  // 4) 10→8bit: dithering + light debanding
  // 5) ICC embedding and validation
}

Measurement Points

• ΔE2000 (skin/sky/green charts)
• Gradient contour detection (SNR/noise metrics)
• Highlight tone preservation (histogram shoulder smoothness)

Pre-Publication Checklist

• [ ] Output color profile matches expectations (sRGB)
• [ ] 8bit quantization artifacts invisible (dither applied)
• [ ] White point consistent across series/features

FAQ

Q. P3→sRGB conversion loses saturation — A. Apply small LCh saturation compensation, masked gently in skin regions.

Q. 8bit banding persists despite processing — A. Use blue noise dithering with weak Gaussian, re-evaluate after output.

Q. Appearance varies across devices — A. Unify ICC presence/absence, QA assuming viewing environment calibration differences.