LumaFlux: Lifting 8-Bit Worlds to HDR Reality with Physically-Guided Diffusion Transformers

arXiv cs.CV / 4/6/2026

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Key Points

LumaFluxは、SDR（8-bit）をHDR（10-bit）へ変換するための物理・知覚ガイド付き拡散トランスフォーマー（DiT）で、従来の逆トーンマッピングが抱える一般化不全（ハイライトのクリップ、色の脱飽和、不安定な再現）を改善することを狙っています。
物理ガイダンスとしてはPGAモジュールが輝度・空間記述子・周波数手がかりを注意機構に低ランク残差で注入し、知覚の安定化としてPCM層が視覚エンコーダ特徴からFiLM条件付けして色（クロマ）とテクスチャを安定させます。
物理信号と知覚信号を融合するHDR Residual Couplerに加え、ハイライトや露光の拡張を行う合理二次スプライン（RQS）デコーダを用いて、VAEデコーダ出力のHDR品質を高めます。
学習の頑健性のため初の大規模SDR-HDR学習コーパスと、HDR参照とエキスパート評価付き劣化SDRを対応付けた新しい評価ベンチマークを構築し、既存SOTAを上回る輝度再構成と知覚的な色忠実度を示したとしています。

Abstract

The rapid adoption of HDR-capable devices has created a pressing need to convert the 8-bit Standard Dynamic Range (SDR) content into perceptually and physically accurate 10-bit High Dynamic Range (HDR). Existing inverse tone-mapping (ITM) methods often rely on fixed tone-mapping operators that struggle to generalize to real-world degradations, stylistic variations, and camera pipelines, frequently producing clipped highlights, desaturated colors, or unstable tone reproduction. We introduce LumaFlux, a first physically and perceptually guided diffusion transformer (DiT) for SDR-to-HDR reconstruction by adapting a large pretrained DiT. Our LumaFlux introduces (1) a Physically-Guided Adaptation (PGA) module that injects luminance, spatial descriptors, and frequency cues into attention through low-rank residuals; (2) a Perceptual Cross-Modulation (PCM) layer that stabilizes chroma and texture via FiLM conditioning from vision encoder features; and (3) an HDR Residual Coupler that fuses physical and perceptual signals under a timestep- and layer-adaptive modulation schedule. Finally, a lightweight Rational-Quadratic Spline decoder reconstructs smooth, interpretable tone fields for highlight and exposure expansion, enhancing the output of the VAE decoder to generate HDR. To enable robust HDR learning, we curate the first large-scale SDR-HDR training corpus. For fair and reproducible comparison, we further establish a new evaluation benchmark, comprising HDR references and corresponding expert-graded SDR versions. Across benchmarks, LumaFlux outperforms state-of-the-art baselines, achieving superior luminance reconstruction and perceptual color fidelity with minimal additional parameters.