Color Pipeline Basics: Rec.709, HDR and ACES

The Short Answer

A color pipeline is the chain of decisions about how an image is interpreted from camera to screen. Every stage needs two answers: what color space and brightness curve the picture is in, and what the next stage assumes it is in. Rec.709 is the standard for HD television and most web video. HDR formats such as PQ and HLG carry a much wider brightness range. ACES is a system that sits in the middle, so footage from many cameras can be graded in one place and then rendered for many outputs. Most color problems on small projects come from a mismatch between two stages, not from the grade itself.

Three Ideas Behind Every Pipeline

1. 1Primaries and white point decide which colors the image can hold. Rec.709 and sRGB share the same primaries and white point.
2. 2The transfer function decides how brightness values are encoded, which is what we usually call gamma or log. Rec.709 and sRGB differ here, and that difference causes a lot of confusion.
3. 3Scene-referred versus display-referred. A camera log file describes the light in the scene. A Rec.709 file describes what should appear on a display. Going from one to the other needs a deliberate conversion, not a guess.

Rec.709 in Plain English

Rec.709 (ITU-R BT.709) is the standard for HD video, with its own primaries and a camera-side transfer curve. When people grade for a reference monitor in a dark room, they normally target a display gamma of about 2.4, which is described in ITU-R BT.1886. Computers and phones in bright rooms often use an sRGB curve that approximates gamma 2.2.

That is why the same file can look different in different players. The best known case is the QuickTime gamma shift: a file tagged Rec.709 can look lighter or flatter in QuickTime or a browser than in your grading software, depending on the codec, the operating system, the application's color management and how the file is tagged. Our post on Premiere export color shift in QuickTime and YouTube covers the practical fixes.

HDR in Plain English

HDR formats describe a much wider range of brightness than SDR.

• PQ (SMPTE ST 2084) encodes absolute brightness and underlies HDR10 and Dolby Vision. A display shows the brightness the file asks for, within its limits, so the mastering display and the metadata matter.
• HLG (hybrid log-gamma) is relative and designed so one signal can work on both HDR and older SDR sets, which is why it is used in broadcast.
• Rec.2100 is the ITU specification that defines HDR for television with both PQ and HLG.

HDR grading needs a monitor that can actually show the range you are delivering, a controlled room, and tools that handle metadata. A laptop screen set to HDR is not a reference. Many buyers require specific HDR formats and mastering display settings for HDR deliveries, so check their delivery spec before you decide to grade in HDR. A project can be graded in HDR first and trimmed for SDR, or the other way around, and the choice affects the schedule.

ACES in Plain English

ACES, the Academy Color Encoding System, is an open standard for managing color from capture to archive. The Academy's documentation says it aims to keep the creator's intent consistent through editing, VFX, mastering and archiving, and to make files easier to exchange. It works like this:

1. 1Input conversions (IDTs) bring each camera's footage into a common space. You pick the one for each camera.
2. 2A working space is where grading and compositing happen. ACEScct is a log-style encoding made for grading, and ACEScg is used in CG and compositing. ACES2065-1 is the interchange and archival encoding.
3. 3Output rendering turns the image into what a given display should show: Rec.709, P3, HDR. ACES 2 changed the design of the rendering step, so check which version your tools and your colleagues use.
4. 4Look conversions (LMTs) are optional creative looks that can be applied before the output rendering.
5. 5ACES Metadata File (AMF) and Common LUT Format (CLF) are file formats for carrying the settings and looks between systems.

ACES is not a look, and it does not fix badly exposed footage. Its value is in a predictable pipeline across cameras, vendors and deliveries.

Do You Need ACES?

DaVinci Resolve offers both its own color managed workflow (DaVinci YRGB Color Managed) and ACES. Menu names change between versions, so follow the current Blackmagic manual rather than a screenshot from an older video. Resolve users should also know that setting the ACES output device to None delivers ACES 2065-1 images, not a display-ready file, as one Netflix help article points out.

Where Mistakes Creep In

1. 1Wrong or missing input conversion. Footage looks flat or too contrasty because a log camera is treated as Rec.709, or the other way round.
2. 2Double conversions. A LUT is applied on set, burned into proxies, and applied again in the grade.
3. 3Mixed sources on one timeline without per-clip input settings.
4. 4Monitoring errors. A computer display with wrong profile, a monitor set to a different gamma than the grade, or a TV with motion smoothing and picture modes.
5. 5Export tags. Delivering a file with missing or wrong color tags, so a player guesses.
6. 6Proxies. Proxies made without the same color treatment as the camera files cause confusion in review.
7. 7Different software, different defaults. Premiere, Resolve and an online reviewer may each display the same file differently.
8. 8HDR to SDR conversion by guesswork. Use a proper conversion or a dedicated trim pass.
9. 9Review links. Reviewers watch on phones and laptops, so tell them what they are looking at.

A Short Checklist for Small Teams

• Write down the camera color settings, input conversions, working space, display target and delivery spec on one page.
• Lock the pipeline before the edit starts, and use it for proxies and dailies as well.
• Test with one clip through the whole path, from camera to final export to the platform.
• Calibrate or check the reference monitor, and grade in a consistent room.
• Export with correct color tags, then check on a phone, a laptop and a TV.
• Keep the project settings with the archive. See archiving a finished film.
• Read color grading for social media video when the output is web and mobile.

Want a person to help?

Our production consulting team designs color suites and pipelines for small teams, including monitoring, calibration, storage and review. See our color suite consulting, or tell us about your pipeline and a real person on our team will reply.