16-bit Linear Mastering & DaVinci Resolve / ACEScg Cinema Workflow

In professional film digitization, the designated role of an export format dictates the degree of creative latitude available during downstream color grading. Conventional inversion utilities typically produce display-referred finished deliverables, such as 8-bit JPEG files or standard TIFFs encoded with sRGB display transfer functions. Prior to export, these files bake in internal tone curves, print film emulation lookup tables, highlight rolloff compression, and monitor electro-optical transfer functions (OETFs). When a colorist subsequently attempts substantial exposure adjustments or shadow recovery, the image degrades rapidly with tonal posterization, hue shifts, and amplified sensor noise.

In contrast, Linear Mastering Delivery provides scene-referred intermediate deliverables tailored for theatrical post-production pipelines. The core mechanism involves tapping the data stream immediately following optical inversion and primary working space projection, prior to the application of any display curves or perceptual color grading.

NexFilm Core Processing Pipeline
┌────────────────────────────────────────────────────────┐
│  Transmittance -> Net Density -> Printer Lights -> Inversion │
└──────────────────────────┬─────────────────────────────┘
                           │
                           ▼
               [ Linear Truncation Tap ]
              /                         \
             /                           \
     [ Lossless Master Exports ]      [ Display Render Pipeline ]
     - 16-bit Linear TIFF             - Four-channel tone curves
     - LinearRaw DNG                  - Print film LUTs (Kodak 2383)
     - Raw Mosaic DNG                 - Spatial sharpening & tone mapping
     (Linear gamma / full range)      - sRGB / Display P3 OETF encoding
             │                        - 8/16-bit TIFF / JPEG delivery
             ▼
     DaVinci Resolve / ACEScg

Exported through this linear truncation point, a 16-bit Linear ProPhoto RGB raster maintains pixel values that remain strictly proportional to original positive scene irradiance. This representation yields grading latitude equivalent to digital cinema camera raw footage (such as ARRI ALEXA LogC or RED Log3G10). In DaVinci Resolve, colorists can grade these wide-gamut, uncompressed positive rasters with full secondary control and color management fidelity.

To satisfy diverse post-production requirements and long-term archival standards, the NexFilm backend (src/dng_writer.rs and src/commands.rs) implements three lossless mastering configurations:

1. 16-bit Linear TIFF:
   Upon completing net optical density inversion and base subtraction, the raster transforms into Linear ProPhoto RGB floating-point radiance and quantizes directly to uncompressed 16-bit integer TIFF. The file records an identity gamma of 1.0 alongside standard ROMM RGB chromaticity coordinates. This format provides the cleanest interchange standard for immediate ingestion into DaVinci Resolve, Nuke, or Baselight.
2. LinearRaw DNG:
   For workflows coordinated through Adobe Camera Raw or Lightroom, users can export as LinearRaw DNG. Structured as a TIFF/EP container, the file writes PhotometricInterpretation = 34892 (LinearRaw) and embeds calibrated D50 and D65 color matrix tags. Third-party raw developers recognize the file as an un-demosaiced linear raw capture, allowing flexible adjustments of color temperature, white balance, and chromatic lens corrections.
3. Raw Mosaic DNG:
   Tailored for archival institutions requiring strict preservation of original digitizer sensor data. Rather than performing demosaicing or non-linear adjustments, the engine re-wraps raw Bayer or X-Trans color filter array photosite samples directly into a compliant DNG container (PhotometricInterpretation = 32803 (CFA)). Hardware metadata, black levels, and white balance multipliers are preserved verbatim, guaranteeing uncompromised re-processing in future decades.

When importing NexFilm 16-bit Linear ProPhoto RGB masters into DaVinci Resolve, technical colorists should utilize color-managed pipelines to maintain consistent color rendering:

Approach A: DaVinci YRGB Color Managed Pipeline (Recommended for Commercial Facilities)

1. Navigate to DaVinci Resolve Project Settings -> Color Management.
2. Configure Color Science to DaVinci YRGB Color Managed.
3. Clear the Automatic color management checkbox and select Custom for the Color processing mode.
4. Input Color Space: Set to Linear transfer function with ProPhoto RGB (or ROMM RGB) chromatic primaries.
5. Timeline Color Space: Configure as DaVinci Wide Gamut / Intermediate. All grading operations throughout the node tree will execute within this high-dynamic-range logarithmic space.
6. Output Color Space: Select according to the mastering monitor target (e.g., Rec.709 Gamma 2.4 for SDR broadcasting, or P3-D65 ST2084 1000 nits for HDR mastering).

Approach B: Academy Color Encoding System (ACES) Pipeline (Recommended for Cinema Post)

1. In Project Settings, select Color Science as ACEScc or ACEScct (with ACEScct preferred for its smooth, photographic toe behavior in deep shadows).
2. ACES Version: Specify ACES 1.3.
3. ACES Input Transform (IDT): Because Linear ProPhoto is not an embedded camera profile, set the global IDT to No Input Transform. Input transformation is applied explicitly via node-based Color Space Transform plugins.
4. ACES Output Transform (ODT): Set to match the calibrated theatrical projection or mastering monitor standard (such as Rec.709 or DCI-P3 D65).

With the color management baseline established, colorists can construct a structured node graph. The recommended node structure separates primary balancing from localized creative stylization:

[Node 01: CST Input] -> [Node 02: Exposure Offset] -> [Node 03: Contrast Curve]
                                                            │
                                                            ▼
[Node 06: Output Transform] <- [Node 05: Film Grain] <- [Node 04: Secondaries]

Detailed operational guidelines for each node:

1. Node 01: Input Color Space Transform (CST)
   Under an ACEScct project setup, load the Color Space Transform OFX plugin on the primary node. Set Input Color Space to ProPhoto RGB and Input Gamma to Linear. Set Output Color Space to ACEScg and Output Gamma to ACEScct. Ensure Tone Mapping is set to None to prevent uncalibrated compression.
2. Node 02: Logarithmic Exposure & Printer Lights Balancing (Offset Wheel)
   Within ACEScct log space, adjustments made on the Offset color wheel correspond to additive optical filtration changes on a traditional motion picture contact printer. This control shifts the exposure linearly without introducing saturation distortion or highlight clipping.
3. Node 03: Film Emulsion Contrast Curve (Custom Curves)
   Construct an S-shaped sensitometric curve emulating photographic print paper characteristics. Refine the highlight shoulder roll-off and shadow toe threshold to build optical negative depth.
4. Node 04: Secondary Qualification & Skin Tone Isolation
   Utilize HSL qualifiers or 3D volumetric isolation masks to isolate subject skin tones or atmospheric sky values, purifying subtle tonal imbalances without affecting background neutrals.
5. Node 05: Organic Texture & Halation Modeling
   Apply photochemically calibrated film grain or optical halation plugins to introduce physical silver halide grain texture and dye dispersion.
6. Node 06: Output Limiting & Gamut Clamping
   Verify that all luminance signals conform to broadcast or theatrical delivery specifications without out-of-gamut clipping.

To assist post-production supervisors in selecting appropriate export formats, the table below outlines the core parameters and intended applications across the NexFilm export matrix: