Apple caps SDR brightness at 500 nits on the M-series MacBook Pros and Pro Display XDR, even though the panels can hit 1,600. Vivid pretends the whole desktop is HDR content so the display lets the extra headroom out — toggle it from the menu bar or with a hotkey, then drive it from the regular brightness keys. Outdoors on a sunny patio it’s the difference between a usable laptop and a mirror; €20 one-time, no subscription.