HDR and Color Management

WATCHOUT manages color from media decode, through compositing, to the signal sent to each display. The same pipeline handles both standard dynamic range (SDR) and high dynamic range (HDR). Color space, transfer function, and bit depth are set per display.

Color management keeps colors looking the way they should on every screen in your setup. SDR is standard brightness, what most screens have shown for years. HDR allows much brighter highlights and deeper darks, closer to what your eyes see in the real world.

WATCHOUT uses 200 nits as the default peak brightness for SDR and sRGB content. This is the level SDR white maps to, and the reference for placing SDR content on an HDR display.

The Color Pipeline

Every pixel travels from source decode, through linear wide-gamut compositing, to the signal each display receives — see Color Pipeline for how that works. The settings on this page configure the final output stage: the color space, transfer function, and bit depth of the signal sent to each display.

Color Spaces

A color space sets the range of colors (the "gamut") that can be shown. Select one per GPU display in Device Properties → Output → Signal.

sRGB and Rec. 709 cover a relatively narrow range, suitable for conventional displays. Rec. 2020 covers a much wider range, for more saturated color. The display hardware must support the wider gamut for it to make a visible difference.

  • sRGB — the standard for computer displays. Rec. 709 primaries with the sRGB curve.
  • sRGB (gamma 2.2) — sRGB primaries with a plain 2.2 gamma curve. The default for new displays.
  • Rec. 601 — the legacy standard-definition space, for SD or older equipment.
  • Rec. 709 — the HD broadcast standard. Use this for broadcast outputs and SDI feeds.
  • Rec. 2020 — a wide-gamut space for UHD content. No display reproduces the full gamut yet, so it serves as a target for the best available hardware.
  • Rec. 2100 PQ — Rec. 2020 primaries with the PQ curve. The basis of HDR10 delivery.
  • Rec. 2100 PQ (HDR10) — the same, with HDR10 static metadata (MaxCLL, MaxFALL) signaled. Use this when the display expects HDR10 metadata.
  • Rec. 2100 HLG — Rec. 2020 primaries with the HLG curve. Common in live broadcast HDR.
The Rec. 2020 triangle covers a significantly larger area of visible colors than the standard sRGB space.

Transfer Functions

A transfer function is the agreed curve that links signal values to displayed brightness. WATCHOUT encodes the output signal with the OETF for the chosen color space. The display reverses it with its EOTF to recreate the intended brightness.

Your eyes notice small steps in dark shades more than in bright ones. A transfer function spends more signal precision on the darks and less on the brights, which reduces visible banding. sRGB, PQ, and HLG are different strategies for this, each for a different situation.

WATCHOUT applies the curve that matches the display's color space:

  • sRGB — the standard curve for computer displays. Linear near black, power-law above.
  • Gamma 2.2 — a plain 2.2 power curve. Simpler than sRGB and often used as a close approximation of it.
  • SDR — the Rec. 709 broadcast curve, for Rec. 709 and Rec. 601 outputs.
  • PQ — an absolute curve covering 0–10,000 nits. Used with Rec. 2100 PQ and HDR10.
  • HLG — a relative curve, backward-compatible with SDR in its lower half. Used with Rec. 2100 HLG.

The transfer function follows the color space automatically. Selecting Rec. 2100 PQ uses the PQ curve.

Compare how different transfer functions map signal values to luminance. Note the logarithmic scale on the Y-axis. PQ is absolute (the signal encodes real nits, up to 10,000). The SDR curves and HLG are relative, shown scaled to their reference peaks (SDR 200 nits, HLG 1000 nits).

Display Color Depth

Color depth sets how many bits are used per color component in the output signal. Higher bit depth reduces banding, which matters most for HDR.

Bit depth is like the number of steps between two colors. With few steps (8-bit) you may see bands in a gradient like a sunset sky. More steps (10-bit or higher) make the transition smooth.

  • GPU outputs — 8, 10, 12, or 16 bpc (bits per component).
  • SDI and ST 2110 outputs — 8 or 10 bpc.

PQ-encoded HDR needs at least 10 bpc to avoid visible banding in dark gradients. Set color depth in Device Properties → Output → Signal, and match it to what the display hardware supports.

Select a lower bit depth (e.g., 8 bpc) and increase Zoom to see quantization banding artifacts in the dark gradients.

SDR White Point (Per-Cue)

When SDR content plays on an HDR display, WATCHOUT needs to know how bright SDR "white" should appear within the HDR range. The SDR White Point property on a media cue sets this.

Placing a white SDR text label on an HDR display can look very dim, especially against bright HDR scenes. Increase the cue's SDR White Point to bring the label up to the look you want.

The value is in nits and ranges from 80 to 10,000. The default is 200 nits, which suits most projection and LED setups. A value of 100 nits matches content mastered to broadcast SDR.

This setting only takes effect when the display uses an HDR color space. On SDR displays it has no impact.

HDR HEADROOM
0 nits (SDR Black)
10,000 nits
203 nits
SDR White
Adjust the SDR White Point to define how bright standard content appears.
The hatched area shows the remaining HDR Headroom for highlights.

Per-Display Color Settings

Each GPU display has independent color settings in Device Properties → Output → Signal:

  • Color Space — the target color space and transfer function (the list above).
  • Color Depth — the output bit depth.

These tell the renderer what to output. They must match the display hardware. Setting an HDR color space on a display that only supports SDR gives incorrect color.

White Point Calibration

Each display has a White Point setting with separate Red, Green, and Blue sliders (0.0 to 1.0, default 1.0). Use it to match color temperature across projectors in a multi-projector setup.

When adjacent projectors look slightly different (one warmer, one cooler), adjust the sliders until the white tones match. For example, if a projector looks too blue, lower its Blue slider until it matches its neighbours.

Multi-display color consistency: match color temperature across all outputs using the white point sliders. Work with a neutral test image (a gray ramp or white field) under final show lighting. Lock display settings once calibration is approved to prevent accidental changes.

Asset Color Space

Some media files include color metadata that tells WATCHOUT how to read the source pixels, and WATCHOUT reads it during decode. When a file has no color metadata, WATCHOUT applies a default color space, set to match the most common content.

If the color space is wrong, correct it by creating a new version of the asset with the right color space. Accurate color space matters: a Rec. 2020 asset read as Rec. 709 comes out desaturated. The asset's color space is shown in the asset properties.

Some image and video files carry color metadata; some do not. When it is missing, WATCHOUT falls back to a default color space, chosen to suit the most common content. If colors look wrong, create a new version of the asset and set the correct color space.

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