Color Spaces

Why color spaces matter

Every image has a color space — a mathematical description of how its pixel values map to actual light. A JPEG from your phone is sRGB. A log clip from an ARRI is LogC3. If you apply a grade without accounting for the source color space, the result is incorrect: contrast curves hit the wrong tonal zones, saturation shifts look wrong, and the overall look doesn't translate between images.

Cineon's ACES effect handles all of this explicitly. You tell it what your image is, and it converts to a linear working space before any other effect touches the pixels.

The ACES pipeline

ACES (Academy Color Encoding System) is the industry-standard color management framework used in cinema, VFX, and high-end photography. Cineon implements ACES 1.3.1 as a WebGPU compute shader — a 1:1 port of the reference implementation running fully on your GPU.

The pipeline has three stages:

Input image
    ↓
[Input Transform] — decode log / convert gamut → ACEScg linear
    ↓
[RRT] — Reference Rendering Transform (scene-linear → OCES)
    ↓
[ODT] — Output Display Transform (OCES → display space)
    ↓
Canvas / Export

Working space

Cineon always works in ACEScg (AP1 primaries, linear light). This is the same working space used in professional VFX and DI pipelines. All effects — grain, halation, color grading, LUTs — operate on the ACEScg linear buffer.

Input gamuts

The Input Gamut parameter tells ACES what color space your source image is in. Cineon decodes it to ACEScg linear before processing.

Log decoding

Log formats compress a wide dynamic range into a smaller code value range. Cineon decodes each log format using its official spec:

• LogC3 — ARRI official cut/slope parameters (cut = 0.1497, a = 5.5556, b = 0.0523)
• SLog3 — Sony official 10-bit normalized spec (threshold = 171.2103/1023)
• CLog2 — Canon official formula with symmetric negative handling
• RED — RED Log3G10 formula (a = 0.224282, b = 155.9753, g = 15.1927)

After decoding to linear scene light, each log format is multiplied by its native gamut-to-AP1 matrix to land in ACEScg.

Display transforms (ODT)

The Display ODT parameter controls how the graded ACEScg image is converted for your monitor.

The RRT (Reference Rendering Transform) runs between ACEScg and the ODT. It applies a cinematic tone mapping curve — lifting shadows slightly, rolling off highlights — that mimics the response of photochemical print film. This is what gives the ACES look its characteristic contrast.

Bypass ODT

Setting ODT to Bypass skips both the RRT and the display transform. The raw ACEScg working space is displayed on the canvas. This is useful for:

• Checking your grade in linear light before tone mapping
• Grading material that will be composited downstream
• Exporting to a DCP or VFX pipeline that expects scene-linear

EV and Bias

Two exposure controls sit inside the ACES effect, applied at specific points in the pipeline:

Both are in stops (2^EV and 2^Bias multipliers). EV affects the tone mapping response; Bias is a pure post-grade brightness offset.

Treat Display as Scene

This toggle changes how display-referred inputs (sRGB, Rec.709, P3, Rec.2020) are handled when passed through ACES.

• On (default) — the input is converted to ACEScg via a matrix transform, treating it as if it were scene-linear. This is the standard path and gives the most consistent ACES look.
• Off — reserved for future InvRRT path (not yet implemented on GPU). Currently falls back to the same scene path.

For most users: leave this on.

Conversion effect

The Conversion effect is a lighter-weight alternative to ACES for simple color space changes. It converts your image to a target display profile at a given strength — useful for quick looks without the full ACES pipeline.

It does not apply an RRT, does not decode log, and does not use a linear working space. Use ACES for accurate color science; use Conversion for artistic looks.

Recommended workflows

Camera phone / JPEG → final grade

Input Gamut: sRGB → ODT: sRGB

Standard path. ACES applies a slight cinematic contrast curve on top.

ARRI log footage → grade → web export

Input Gamut: LogC3 → ODT: sRGB

Full log decode + ACES RRT. Highlights roll off smoothly, shadows open up naturally.

Sony mirrorless (SLog3) → grade → video export

Input Gamut: SLog3 → ODT: Rec.709

Broadcast-correct output for YouTube or Vimeo.

VFX / compositing — keep scene-linear

Input Gamut: ACEScg → ODT: Bypass

Pass-through. Grade without tone mapping for downstream compositing.