Color Grade Resolve

Skill: Color Grade (DaVinci Resolve)

Generate DaVinci Resolve node-based color corrections. Resolve uses a node graph instead of stacked effects - each node is an independent corrector with its own primaries, curves, qualifier (HSL Secondary), power windows, and LUT.

Node Order

Follow this professional node order for serial node chains. Each node serves one purpose:

1. White Balance — Correct color temperature and tint first, before any other processing
2. Exposure — Set overall exposure/gain to get correct brightness levels
3. Main Conversion LUT — Apply camera-to-display transform (e.g., ARRI LogC to Rec.709)
4. General Color Adjustments — Lift/Gamma/Gain wheels, contrast, color balance
5. Color Saturation/Boost — Global and selective saturation adjustments
6. Noise Reduction — Temporal and spatial NR (do this before sharpening)
7. Black Levels — Crush or lift blacks, set floor
8. Vignette — Power window with soft edge for light falloff
9. Sharpening — Always last - sharpens the final result

Not every grade needs all 9 nodes. Skip nodes that aren't needed. For qualifier-based (HSL Secondary) corrections like skin fixes, insert additional nodes between steps 5 and 6 with the qualifier keyed to the target zone.

Resolve API Capabilities

The scripting API (Python/Lua, requires Resolve running) supports:

• SetCDL({NodeIndex, Slope, Offset, Power, Saturation}) — ASC CDL values per node
• SetLUT(nodeIndex, lutPath) — Apply .cube LUT to a specific node
• ApplyGradeFromDRX(path, gradeMode) — Apply a saved grade still (DRX) to clips
• ExportLUT(exportType, path) — Bake grade to .cube file
• GrabStill() / ExportStills() — Save grades as DRX stills

Not available via API: Creating/adding nodes, setting color wheels directly, setting qualifiers/HSL keys, setting curves. These require either DRX files or manual work in the Color page.

Workflow

Option A: DRX Grade Stills (Full Node Graph)

If a DRX file is available (exported from Resolve with a reference grade):

1. User creates reference grade manually in Resolve's Color page
2. Export as DRX: Gallery → right-click still → Export → .drx
3. Apply to all clips via script:

# apply_grade.py — run with Resolve open
import DaVinciResolveScript as dvr
resolve = dvr.scriptapp("Resolve")
project = resolve.GetProjectManager().GetCurrentProject()
timeline = project.GetCurrentTimeline()
clips = timeline.GetItemListInTrack("video", 1)
timeline.ApplyGradeFromDRX("/path/to/grade.drx", 0, clips)

Option B: CDL + LUT (Basic Corrections)

For grades that can be expressed as CDL values + a LUT:

1. Analyze frames with analyze_frame.rb (same as Premiere workflow)
2. Calculate CDL slope/offset/power from desired corrections
3. Generate a Python script that applies CDL + LUT per node:

import DaVinciResolveScript as dvr
resolve = dvr.scriptapp("Resolve")
project = resolve.GetProjectManager().GetCurrentProject()
timeline = project.GetCurrentTimeline()
clips = timeline.GetItemListInTrack("video", 1)
for clip in clips:
    # Node 1: White Balance (via CDL offset)
    clip.SetCDL({"NodeIndex": "1", "Slope": "1.0 1.0 1.0", "Offset": "0.0 0.0 0.0", "Power": "1.0 1.0 1.0", "Saturation": "1.0"})
    # Node 3: Main LUT
    graph = clip.GetNodeGraph()
    graph.SetLUT(3, "AMIRA_Default_LogC2Rec709.cube")

Option C: Frame Analysis + Manual Guide

When API isn't sufficient (need qualifiers/HSL Secondary):

1. Analyze frames with analyze_frame.rb to get HSV stats per zone
2. Generate a detailed correction guide with specific values for the colorist:
   • Per-node settings following the node order above
   • Qualifier key ranges (hue center/range, sat center/range, lum center/range)
   • Correction values for each keyed zone
3. User applies manually in Resolve's Color page using the guide

Option D: Custom .cube LUT Generation (No Studio Required)

Generate targeted correction LUTs programmatically using generate_lut.rb. Presets are config-driven via presets.yml — add new LUT types by editing YAML, no Ruby changes needed. These work in both Resolve and Premiere with no API or Studio dependency.

# Remove warm amber/yellow cast from stage lighting
ruby generate_lut.rb yellow_fix /path/to/output.cube

# Roll off overexposed skin highlights (only affects lum > 70%)
ruby generate_lut.rb skin_highlight_fix /path/to/output.cube

# Adjust strength (0.0-1.0)
ruby generate_lut.rb yellow_fix /path/to/output.cube --strength=0.5

# Compare reference vs output and get adjustment suggestions
python3 match_grade.py <reference.png> <output.png>

To create a custom preset, add an entry to presets.yml with a pipeline of steps (exposure, black_crush, skin_correction, hue_desat, etc.) and run ruby generate_lut.rb my_preset output.cube.

Available LUT types:

• yellow_fix — Targets H=10°-60° (warm amber/yellow), reduces saturation 55%, shifts hue toward neutral. For stage lighting spill.
• red_skin_fix — Fixes sunburnt/flushed red skin from warm practical lights. Shifts red skin hues toward peach. Only targets skin luminance+saturation range — leaves light sources, deck, and saturated objects alone.
• night_warm_fix — All-in-one for underexposed warm/red practical scenes. ~1 stop lift + skin hue shift + black crush. No desaturation.
• night_purple_fix — All-in-one for underexposed purple/magenta stage lighting. RGB channel rebalancing (boost G, reduce B) + ~2 stop lift + purple desaturation + skin hue shift from purple toward natural + black crush. Preserves atmospheric purple from stage lights while making skin look natural. Developed for SSMC 2025 salsa performances.
• overexposure_fix — Scene-wide ~1 stop reduction with highlight rolloff from 55%. For blown-out footage.
• underexposure_fix — Scene-wide ~1.2 stop lift with shadow recovery and highlight protection. For dark footage.
• black_crush — Crushes milky/lifted blacks below 12% luminance to true black.
• skin_highlight_fix — Subtle skin-only rolloff above 70% luminance. For minor skin overexposure.
• golden_warm — Strong golden warm shift via RGB rebalance (R:1.20, G:1.00, B:0.80). For rich warm cinematic looks.
• cinema_dark — Deep moody contrast with gamma 1.45, shadow lift 0.02, and knee compression (0.72-0.90). For dramatic, filmic contrast.

Node chain building blocks (studio_punch, film_contrast, cinema_dark, warm_shift, golden_warm, cool_shift, sat_boost, sat_reduce, etc.) can be combined via generate_chain_lut.rb to bake multi-preset chains into a single .cube LUT — including conversion + creative in one pass.

Creative presets available in the interactive preview:

• Studio Clean — studio_punch(50%) + sat_boost(50%)
• Studio Balanced — studio_punch(80%) + warm_shift(30%) + sat_boost(50%) + black_crush(15%)
• Studio Ambient — studio_punch(80%) + warm_shift(100%) + sat_boost(100%) + black_crush(20%) — for no-fill-light scenarios
• Studio Gold — cinema_dark(80%) + golden_warm(75%) + sat_boost(100%) + black_crush(10%) — warm cinematic
• Studio Dance — studio_punch(100%) + warm_shift(40%) + sat_boost(60%) + black_crush(25%)
• Studio Film — film_contrast(60%) + warm_shift(20%) + sat_reduce(30%) + black_crush(40%)

All LUTs support --strength=N (0.0-1.0) for intensity control.

Apply in Resolve: add node after conversion LUT → right-click → LUT → browse to .cube file. Apply in Premiere: Lumetri Color → Creative → Look dropdown → browse.

Option E: Match Grade Analysis

match_grade.py compares a reference image against an output image and suggests preset adjustments to bring the output closer to the reference. Useful for matching grades across clips or iterating toward a target look.

python3 match_grade.py <reference.png> <output.png>

Scripting Setup (Windows)

RESOLVE_SCRIPT_API=C:\ProgramData\Blackmagic Design\DaVinci Resolve\Support\Developer\Scripting
RESOLVE_SCRIPT_LIB=E:\Davinci Resolve\fusionscript.dll
PYTHONPATH=%PYTHONPATH%;%RESOLVE_SCRIPT_API%\Modules\

Resolve must be running for scripts to connect.

Key Reference

CDL parameters map to Resolve's primary corrections:

• Slope — Multiplier (like Gain). "1.0 1.0 1.0" = neutral. "1.2 1.0 0.9" = warmer
• Offset — Added value (like Lift). "0.0 0.0 0.0" = neutral
• Power — Gamma curve. "1.0 1.0 1.0" = neutral. Higher = brighter midtones
• Saturation — Global sat. "1.0" = neutral. "0.0" = monochrome

Color Science Fundamentals

Key concepts for understanding what the LUT generator does and how to create new correction types:

Color Spaces

• Rec.709 — Standard HD display color space. Small gamut, fixed gamma. What the audience sees.
• Log curves (ARRI LogC, Sony S-Log3) — Logarithmic encodings that compress maximum dynamic range into a video signal. Look flat by design. Each camera manufacturer has their own curve.
• ACES — Academy Color Encoding System. Scene-referred, open framework. Pipeline: Input Transform → ACES → RRT → ODT → Display. Future-proof, encompasses full human vision.

How LUTs Work

• 1D LUT — Per-channel curve (like Photoshop Curves). Can do brightness, gamma, contrast. No cross-channel interaction.
• 3D LUT — 3D lattice indexed by R, G, B simultaneously. Allows cross-channel operations (changing R output based on G and B input). A 33³ LUT has 35,937 sample points with trilinear/tetrahedral interpolation between them.
• The .cube format is plain text: header + RGB triplets. Simple to generate programmatically.

HSL vs RGB for Corrections

• Desaturating warm tones in HSL produces brown/sepia — this is a mathematical property. Orange desaturated = muddy brown.
• RGB channel rebalancing (reduce R, boost B) cools warm tones toward neutral white — better for temperature correction.
• Hue shifting (rotate in HSL) moves colors without losing vibrancy — best for "sunburnt skin → peach" type fixes.
• Use luminance + saturation windows to isolate skin from light sources and saturated objects at similar hues.

Frame Analysis Workflow for New LUT Development

When fixing a specific clip, follow this workflow to diagnose and build a correction LUT:

1. Extract a frame at the target timecode using ffmpeg:

   # Get starting timecode and frame rate from the clip
   ffprobe -v error -show_entries stream_tags=timecode -show_entries stream=r_frame_rate -of default video.mp4
   # Calculate offset: (target_tc - start_tc) in seconds
   # Extract frame at that offset
   ffmpeg -y -ss <offset_seconds> -i video.mp4 -vframes 1 -vf "scale=1280:-1" tmp/frames/raw_frame.png
   

2. Apply the conversion LUT (e.g., AMIRA LogC→Rec709) to get the Rec.709 starting point:

   ffmpeg -y -i raw_frame.png -vf "lut3d='/path/to/AMIRA_Default_LogC2Rec709.cube'" amira_applied.png
   

   AMIRA LUT location (Premiere Pro): C:\Program Files\Adobe\Adobe Premiere Pro 2025\Lumetri\LUTs\Technical\AMIRA_Default_LogC2Rec709.cube

3. Analyze color regions using Python or analyze_frame.rb to get HSV stats for skin, neutrals, and problem areas. Sample 5-8 regions: skin (multiple faces), ceiling/walls (should be neutral), floor, clothing (white reference), light sources.

4. Identify the correction needed based on the analysis:

   • Warm/amber cast → yellow_fix
   • Red/flushed skin → red_skin_fix
   • Underexposed + warm → night_warm_fix
   • Purple/magenta cast → night_purple_fix
   • If no existing type fits, create a new one following the same pattern

5. Generate and test the correction LUT, applying it after the conversion LUT:

   ruby generate_lut.rb <type> /path/to/output.cube
   ffmpeg -y -i raw_frame.png -vf "lut3d='conversion.cube',lut3d='correction.cube'" result.png
   

6. Iterate by comparing before/after color stats until skin tones are in the H=10-35° range and neutral areas are desaturated. Use match_grade.py to compare against a reference frame and get specific adjustment suggestions.

Key Lesson: Purple vs Warm Cast Correction

Purple/magenta stage lighting (H=270-330°) requires a fundamentally different approach than warm/red casts:

• Warm cast: R channel elevated → fix with HSL desaturation/hue shift in orange range
• Purple cast: R+B elevated, G suppressed → must fix with RGB channel rebalancing FIRST (boost G, reduce B), then HSL corrections

The RGB rebalancing must be luminance-adaptive — scale the gain adjustments by pixel brightness. Very dark pixels (lum < 12%) get minimal rebalancing to avoid wild hue swings. Without this, dark shadows shift from purple to green.

Targeting Skin Specifically in a LUT

Skin tones occupy a narrow band: H=10-35°, S=0.10-0.45, L=0.25-0.75. Light sources, colored objects, and surfaces may overlap in hue but differ in saturation and luminance:

• Light sources: very high luminance (>0.85) or very high saturation (>0.6)
• Dark surfaces (deck/floor): low luminance (<0.20)
• Skin: moderate saturation, mid luminance

Learning Resources

• Color Correction Handbook by Alexis Van Hurkman — the industry-standard textbook
• Blackmagic Official Training — free at blackmagicdesign.com/products/davinciresolve/training
• Cullen Kelly (YouTube) — technically rigorous free color grading education, Netflix/HBO colorist
• MixingLight.com — 1,200+ structured tutorials from working colorists (paid subscription)
• Frame.io ACES Guide — blog.frame.io/2019/09/09/guide-to-aces/ — best ACES primer
• Dado Valentic / Colour Training — colour.training — bridges color science research and practical grading
• Kodak Color Theory Workbook — free PDF from Kodak covering fundamental color theory for motion pictures

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