ACEScg EXR to Rec.709 or sRGB: making review files that match your ACES viewer
7 min read · Checked against Sequency 1.4 · Updated
Short answer
Use the ACEScg → sRGB Quick Preset for computer screens or ACEScg → Rec.709 for grading and broadcast monitors. Both apply the ACES 1.0 SDR output transform, so highlights roll off the way they do in an ACES viewer. A plain conversion, such as choosing sRGB - Display as the output, clips everything above 1.0.
Steps
- 1
Import the ACEScg sequence
Click Import… (⌘I) and choose the folder of EXR frames, or drag it onto the drop area.
- 2
Turn on colour conversion
In the Settings tab, open Color Space and turn on Enable Color Space Conversion.
- 3
Pick a Quick Preset
Click ACEScg → sRGB for desktop and web review, or ACEScg → Rec.709 for editorial and broadcast monitors. If your renderer writes ACES2065-1 (AP0), change Input Color Space to ACES2065-1 afterwards.
- 4
Check the status line
The line under the switch confirms that OpenColorIO is handling the conversion and which output transform is applied.
- 5
Pick the delivery format and export
Choose H.264 or ProRes in Container, set the frame rate, then click Export Selected… (⌘E).
Recommended settings
| Setting | Value | Why |
|---|---|---|
| Web, Slack, desktop review | sRGB - Display / ACES 1.0 - SDR Video | Matches an sRGB ACES viewer on computer screens. |
| Editorial, broadcast monitor | Rec.1886 Rec.709 - Display / ACES 1.0 - SDR Video | Gamma 2.4 Rec.709, the standard for grading suites. |
| Already display-referred EXRs | Rec. 709 or sRGB (Standard) | No tone mapping wanted; values are already graded. |
| Keep scene-linear for comp | ACEScg, written as OpenEXR | Leaves values untouched for the next artist. |
Plain conversion versus the ACES Output Transform
ACEScg is a scene-linear working space. Its values describe light, not screen brightness, so a bright light or emissive surface might sit at 5 or 50. A plain colour space conversion changes the primaries and applies the display curve, then clips anything above 1.0 to white.
The ACES Output Transform (the RRT and ODT in ACES 1.x) is a tone curve designed for exactly this. It compresses highlights, keeps saturated colours from going flat, and is what Nuke, Resolve and most render viewers show when they are set to ACES. Sequency uses OpenColorIO 2.4 with the built-in ACES 1.3 Studio config to apply it.
What the Quick Presets do
When Sequency detects EXR frames it shows Quick Presets under Color Space. ACEScg → sRGB applies the ACES 1.0 SDR output transform for computer screens. ACEScg → Rec.709 does the same for gamma 2.4 Rec.709 monitors. Linear → sRGB is for renders in linear Rec.709 primaries, such as Blender's default.
For a plain conversion without the tone curve, choose an OCIO display colour space such as sRGB - Display directly in the Output Color Space menu.
If colours look wrong
Washed-out and too bright usually means the input was set to a display space while the EXR is scene-linear. Strong colour shifts usually mean the wrong primaries: ACES2065-1 (AP0) and ACEScg (AP1) are both linear but not interchangeable.
If OpenColorIO cannot build the transform you asked for, Sequency stops the export and tells you, rather than writing a file with the wrong colour label.
Questions
- Is this the same ACES transform Nuke and Resolve use?
- It is the ACES 1.0 SDR Video output transform from the ACES 1.3 OpenColorIO Studio config, which is the same transform OCIO-based tools apply for that display and view.
- Can I load my studio's own OCIO config?
- Not in Sequency 1.4. It uses OpenColorIO's built-in ACES 1.3 Studio config, which covers ACES, the main camera log formats and the standard displays.
- Does it work for H.264 as well as ProRes?
- Yes. The colour conversion happens before encoding, so it applies to every output format, including image sequences.