LUT vs CDL vs CST — A Deep Dive

As I've grown in my career, I've tried to learn more and more about color grading, instead of relying on my ArriLikeBladeRunnerMinusOneStop.cube LUT. So in this one, we're deep diving a couple of technical colorist terms so you know how to properly ask for a teal and orange look.

Mental model: three different tools, three different jobs

• CST (Color Space Transform) = the technical mapping between defined gammas (transfer functions) and gamuts (RGB primaries) — e.g., S-Log3/S-Gamut3.Cine → DaVinci Wide Gamut/Intermediate → Rec.709 2.4. It’s math you could invert, not a look.
• CDL (ASC Color Decision List) = a tiny, parametric creative correction (Slope/Offset/Power + Saturation) that assumes you’re already in a known working color space.
• LUT (1D/3D) = a precomputed mapping table (often creative) that expects a very specific input color space and produces a specific output color space. Fast and portable, but blind to context.

Keep normalization (CST/IDT/ODT) separate from intent (CDL/LUT). One tech transform in, one tech transform out.

Color space transform (CST): what actually happens under the hood

A CST decomposes into two parts:

1. Gamut transform (matrix + chromatic adaptation)
   • Map source RGB primaries → destination primaries with a 3×3 matrix.
   • Apply a white-point adaptation (Bradford/CAT02/CAT16) when source and destination whites differ (e.g., D65 vs D60).
   • Many CSTs include gamut compression for out-of-gamut colors (rolls very saturated hues toward the boundary to avoid clipping when shrinking into Rec.709).
2. Gamma/transfer transform (non-linear function)
   • Convert source code values (log, linear, gamma) into destination (e.g., S-Log3 → “scene-linear-ish” → 709 2.4 tone map).
   • For HDR/SDR pivots, a tone-mapping operator manages highlight roll-off (Reinhard, Hable, ACES RRT-like curves).

Editor implications

• A CST is deterministic and invertible (within the tone-map’s limits). That means conform and round-trips behave.
• If your working color management already applies Input → Timeline → Output transforms, you must not add extra “normalize” LUTs. That’s the classic double-709 that blows out the image.

Where CST lives (by NLE philosophy)

• Resolve RCM / ACES: Project-level or node-level Input/Output transforms. Prefer project-level for consistency; use node-level CST for one-off clips.
• Premiere Pro: Newer versions auto-normalize many log formats if you enable color management. Treat that as your CST. If you must use a LUT to normalize, use exactly one, and disable auto transforms.
• Avid: Source Settings → Color Encoding applies the CST/LUT at ingest level. Keep it technical; keep creative separate (or use Baselight Editions).

CDL: the tiny math that travels anywhere

Formula (per channel):

out = ((in × slope) + offset) ^ power then apply sat in a defined luma/chroma space.

• Slope ≈ gain (contrast scale)
• Offset ≈ lift (black bias)
• Power ≈ gamma (midtone pivot)
• Sat = scalar saturation

Precision realities

• CDLs are unitless until you define the space. The same SOP in log vs linear vs 709 yields different pictures. Always bind a CDL to a colorspace tag (“CDL was authored in ACEScct”).
• CDLs are typically stored as floating-point with a few decimals. They are lossless enough for dailies→final; they’re also editable by humans, which is the point.

Where CDL shines for editorial

• It’s the perfect portable intent: small direction that cuts well in dailies and reproduces in final grade.
• You can attach CDLs as sidecar XMLs, embed via ALE/AAF/EDL in traditional pipelines, or bake them during dailies for editorial only.

LUT: tables, interpolation, and traps

1D LUT: One curve per channel (R, G, B). Great for gamma tweaks (log→linear shapers), not for hue-dependent moves.

3D LUT (cube): Samples of the RGB cube (commonly 17³, 33³, 65³). Interpolation (prefer tetrahedral over trilinear) fills in the spaces between samples.

Shaper LUTs & domain

• Because 3D LUTs are low-resolution, you often pre-warp the input with a 1D shaper (e.g., log→linear) so the cube does its work in a more uniform domain.
• This is why many “show LUTs” are two-stage: a 1D shaper + 33³ or 65³ cube.

Limitations

• LUTs don’t know context. If built for S-Log3/SGamut3.Cine, they’re wrong (and sometimes destructive) on LogC/AWG.
• LUTs can clip/quantize: push saturated primaries, you might hit a cube edge and crush detail.
• LUTs are usually not invertible (especially if they encode an output transform). Don’t rely on “reverse LUTs.”

Pro tip

If you must use a creative LUT, place it in the working space after proper normalization. If it secretly includes an output transform (many “709 looks” do), either (a) treat it as your only output, or (b) rebuild the look as parametric nodes/LUT without an ODT.

Order of operations (editor-safe stacks)

A) Color-managed project (recommended)

1. Input transform (CST/IDT): Camera log+gamut → Working (DWG/Intermediate, ACEScct).
2. Primary balance (CDL-style): White/black/midtone; tiny hue bias.
3. Creative look: Either parametric nodes or a LUT built for the working space.
4. Output transform (ODT/CST): Working → Display (Rec.709 2.4 / P3-D65 PQ)

Exactly one input and one output transform. No extra “normalize” LUTs.

B) Non-color-managed project (legacy)

• Pick one route:
  • Use one “tech LUT” as input (Log→709) then add creative CDL/LUT, or
  • Grade in log with CDL/curves and apply one output LUT at the very end.
• Never both. If scopes show blacks at ~0 and highlights hard-clipping before you grade, you probably normalized twice.

Editor workflows per NLE

DaVinci Resolve (best-case, you own the pipeline)

Project Settings → Color Management

• Choose DaVinci YRGB Color Managed (DWG/Intermediate) or ACES 1.3.
• Set Input Color Space per camera (or use clip-level metadata).
• Output to Rec.709 Gamma 2.4 (SDR) or P3-D65/PQ (HDR).

Node graph suggestion

• Node 1: CST only for off-spec clips (graphics, archival).
• Node 2: CDL-style primaries (printer lights or LGG).
• Node 3: Creative look (LUT built for DWG/Int or ACEScct).
• Output: Let the project ODT handle display mapping.

Dailies & editorial

• Render 709 viewing proxies with the ODT baked, CDL applied, and original reels/timecode preserved.
• Save CDL XMLs per scene and stills for reference. In final grade, re-apply CDLs in working space, not on 709 media.

Adobe Premiere Pro (mixed facilities, lots of handoffs)

Color Management

• In Project Settings → General/Color, enable color management so Premiere recognizes camera gammas/gamuts where supported.
• For clips that mis-tag, Interpret Footage → Color Management and set Input LUT/Colorspace once per master clip. Treat that as your CST.

Where to put things

• Master Clip: Apply the technical normalization (Input LUT or interpret-as-colorspace).
• Lumetri (Creative tab): Apply creative LUT or CDL-equivalent tweaks.
• Adjustment layers for show looks across sequences.

Avoid

• Input LUT and a “LOG→709” creative LUT on the same clip.
• The auto Rec.709 tone-map and a normalize LUT.

Strict CDL?

• Premiere isn’t a first-class CDL carrier. For strict show workflows, generate CDL-baked dailies upstream (Resolve/Colorfront) or use a grading plugin (Baselight Editions) that respects CDL XML.

Avid Media Composer (broadcast sensibility)

Source Settings → Color Encoding

• Attach technical LUT (log→working or log→709) here. That’s your CST stage.
• Keep creative intent separate (Color Correction mode, Baselight Editions, or bake it in dailies).

CDL carriage

• Traditional pipelines carry CDL via ALE/AAF + Baselight Editions. If you’re not using Baselight, prefer CDL baked in dailies + stills for intent; keep camera originals untouched for conform.

One clean reference pipeline

• Capture: S-Log3 / S-Gamut3.Cine (scene-referred).
• On-set viewing: One 3D LUT (S-Log3/SG3C → 709 2.4) on monitors only.
• Dailies: CST (S-Log3/SG3C → DWG/Int) → CDL → ODT (→ 709 2.4) → ProRes Proxy/H.264 proxies for editorial.
• Editorial: Cut with proxies; no extra normalizers. Optionally a working-space creative LUT on an adjustment layer for taste.
• Online/Grade: Originals → CST to working → apply CDLs → creative look → ODTs for SDR/HDR; make trims per output.

In a future deep dive, we'll explore how to practically use a CDL to help throughout. And don't get us wrong; when used well, LUTs can make workflows quick and easy, especially if the LUT is chosen from the very beginning of the capture and used on set.

What is your go to color grading tip? Comment below and we'll feature the best tip in our next newsletter.