Hello,
I would like to introduce an update to the Base Curve module: the addition of a third curve, “Cinematic DRT”, loosely based on OpenDRT.
Cinematic DRT (mode 3) is a Display Rendering Transform (DRT) operating in the Oklab color space (UCS). It is designed to deliver organic rendering without hue drift, even under heavy dynamic range compression.
Key points:
Pre-compression Brilliance : To avoid the “neon” look of highly saturated colors (flowers, LEDs, neon signs), the module intelligently reduces their intensity before tonemapping, proportionally to their saturation. This is the Pre-tonescale Brilliance concept borrowed from OpenDRT.
ACES Tonal Mapping : This mode uses the rational approximation of the ACES curve (Stephen Hill / BakingLab). A +0.25 EV compensation factor (1.189f) is applied to correct for the curve’s natural density. Shadow lift and highlight gain are integrated directly into the curve’s power equation for smooth, artifact-free transitions.
Saturation Gate : A mechanism that reduces saturation proportionally to the compression applied by the tonescale: the more a pixel is pushed toward the highlights, the more it loses color. This guarantees clean, neutral whites even under strong contrast : no more cyan skies or yellowish skin tones in overexposed areas.
Perceptual Saturation Boost : A new slider that boosts saturation in the midtones within UCS space, while protecting areas that are already heavily saturated. Its behavior is similar to a vibrance slider.
UCS Saturation Balance : A sigmoid centered on middle gray is used as a tonal mask. It allows selective saturation of shadows while desaturating highlights (or vice versa), simulating the analog film rendering where highlights naturally lose their color.
Highlight Roll-off : A final stage that progressively desaturates pixels exceeding 80% luminance to ensure a smooth transition to display white. This roll-off was previously hard-coded in the module; it is now a slider available across all three modes.
Sources and Technical References
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Oklab color space : Björn Ottosson (2020), A perceptual color space for image processing A perceptual color space for image processing
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ACES tonal curve : approximation (Modes 1, 2 & 3) — Stephen Hill / BakingLab, RRTAndODTFit approximation BakingLab/BakingLab/ACES.hlsl at master · TheRealMJP/BakingLab · GitHub
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ACES 1.0 tonal curve : approximation (Mode 1 : Kinematic) — Krzysztof Narkowicz (2016), ACES Filmic Tone Mapping Curve ACES Filmic Tone Mapping Curve | Krzysztof Narkowicz
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JzAzBz (used in the Kinematic and Dynamic modes of the same module) : Muhammad Safdar et al. (2017), Perceptually uniform color space for image signals including high dynamic range and wide gamut , Optics Express https://opg.optica.org/oe/fulltext.cfm?uri=oe-25-13-15131
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OpenDRT (source of inspiration for the vector norm and pre-tonescale Brilliance) : Jed Smith GitHub - jedypod/open-display-transform: Open Display Transform is a collection of tools and experiments for rendering wide-gamut scene-linear data into an image for an SDR or HDR display device. · GitHub
Greetings from the Luberon, 
Christian