Constrained Color Carrier: Characterization-Preserving Conditional Color Rendering in Multi-Illuminant Camera Profiles

Abstract

In Digital Negative (DNG) multi-illuminant profiles, characterization matrices and nonlinear rendering payloads share condition-dependent interpolation slots, so adding a slot for rendering capacity also introduces an additional characterization state. We introduce Constrained Color Carrier (CCC), which constructs the three pre-serialization ColorMatrix and ForwardMatrix states from the original dual matrix segments while allowing the same shared slots to carry three HueSatMap rendering bases. Condition-specific HueSatMap payloads are solved as numerical preimages of the target through a fixed serialized downstream rendering operator, and carrier selection enforces a preservation bound on the host-effective interpolated characterization. We evaluate CCC on the Sony ILCE-7RM5 Adobe Standard dual-illuminant profile using a white-balance-dependent Standard ColorCorrect target recovered from Phocus 4.0.1 for the Hasselblad X2D 100C. Using Euclidean Oklab error, CCC yields a worst-temperature 95th-percentile preservation error of 0.003857, below the prescribed tolerance of 0.004, and reduces the worst-condition 95th-percentile target error from 0.08208 for the Dual representation to 0.03508. The synthetic Ordinary Triple yields a preservation error of 0.014802 and exceeds the same tolerance. The serialized DNG Camera Profile (DCP) and Extensible Metadata Platform (XMP) artifacts reproduce the final color-table payloads exactly and yield zero numerical difference from solver-side offline execution, showing that the CCC solution is representable within the evaluated serialized profile format.