How it works
Two ways. Industry session lengths.
Red light sessions on the display you already own — a timed session, or red while you work.
1. 15-minute session
Full-screen Maximum Red — Display P3 (1, 0, 0), the closest wavelength this panel can be asked for. The window fades from black through a Metal-only surface; the timer HUD is a separate overlay so SwiftUI cannot flatten HDR. A solid system color fill is not the light source. Brightness to 100%. Night Shift, True Tone, and Accessibility Invert Colors off — Invert Colors blocks Start because the field would be cyan. Sit about 6 inches if comfortable, or pick 30 cm / 18 in in the app — at 18 inches the field is about a fifth as strong. Dock and menu bar hide for the session. Escape or Option-Command-Period exits. This is the default 15-minute session; 10 and 20 minutes are also there. The display stays awake for those clocks so Energy Saver cannot dim the field early.
2. Red filter while you work
The desktop is remapped to red, like an accessibility color filter. Option-Command-R toggles it. Option-Command-Period restores colors and also ends a running session. More time under visible red while you keep using the Mac.
3. Target versus this display
The app shows what the literature asks for versus what this Mac publishes. We match the 10–20 minute practice. We do not invent a fluence we have not measured.
4. Display Boost
Where the system reports Extended Dynamic Range, the renderer uses that headroom. That is how we push XDR-class panels as far as public APIs allow. The session HUD shows the requested envelope versus live system headroom on that display — idle ~1.2× is not a granted envelope. After a Boost session, Light shows whether live headroom stayed idle or opened. Boost is a Pro unlock.