The Patterns Test Generator allows for the quantification, calibration, and validation of displays connected to macOS. Patterns uses Apple’s APIs to render test images in various color spaces, which means it tests the system, not just the display.
The Goal: Optimize the built-in and/or external display to produce an accurate image for content rendered via macOS.
To achieve this, it helps to understand how Apple’s Color Management is designed. In a traditional (single-standard) workflow, a source and display calibrated to the same standard — say, Rec.709 to Rec.709 — will match, preserving the content creator’s intent. That model assumes only one standard is ever on screen at once.
In practice, that’s rarely true: it’s common to have multiple windows on screen at the same time, each carrying content in a different standard — sRGB, Rec.709, DCI-P3, HDR, and so on. To render all of them accurately at once, macOS uses Active Color Management, which applies color management to every pixel of every frame in real time, mapping each source’s color space to the display’s color space individually.
Because source content can arrive in any color space, the display (the destination space) should be set to the largest space it’s capable of, to maximize available color volume. macOS then maps each window’s color space into that larger space, so multiple windows carrying multiple standards are each rendered as accurately as the target display allows.
Apple XDR Fine-Tune Calibration Theory
The introduction of Apple’s XDR (Extreme Dynamic Range) displays brought an entirely new approach to how the display interacts with the operating system. Central to this is the Preset, found in System Preferences > Displays — analogous to the “Picture Mode” or “Picture Preset” found on many of today’s consumer TVs, where each preset is optimized to a specific target.
The Presets menu is organized into three sections:
Apple Presets. This section includes “Apple Display (P3-500 nits)” and, on Pro Display XDR, “Pro Display XDR (P3-1600 nits).” These presets allow user customization of Brightness, Auto-Brightness, and True Tone, and are optimized for displays up to 500 and 1600 nits respectively. Use these in general home and office environments.
Reference Modes. This section consists of reference modes for today’s most-used standards. Selecting one of these updates both the display and the operating system to match. These modes are optimized for controlled viewing environments as defined by ITU-R BT.2100 — use them when image accuracy is critical.
Custom Presets. This section allows the creation and customization of presets to a user-defined target. Here, the display can be optimized to accurately represent any type of content across the various image processing paths, including the ability to adjust Apple’s System Gamma Boost.
For more information on these modes and presets, see: Use presets and reference modes with your Apple display