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Plate II — light by temperature4300 K

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Color temperature 4300 K

Software dim 100%

The ceiling is your brightness slider. A page can ask pixels for warm white; it cannot raise the backlight. Max your OS brightness first — that's the difference between "glow" and "useful light". The dim slider here only goes down (it mixes in black), which is honest math, not a brightness boost.

Setting the light for the job

Video calls — 4300–5000 K, panel just off-camera at face height. Warmer than that flatters but yellows your whites; cooler starts to look clinical.
Desk makeup — match where you're headed: 3200 K for dinner lighting, 5600 K for office daylight. Judging warm makeup under cool light is how surprises happen.
Reading in the dark next to someone asleep — 2700 K at the lowest dim you can still read by. Warm light carries less of the blue band that fights melatonin.
Filling shadows for a photo — 5600 K matches most daylight scenes; bring the panel close, since screen light falls off fast with distance.

What the kelvin number means

Color temperature runs backwards from intuition: lower kelvin is warmer. 2700 K is the orange of a filament bulb, 4300 K sits neutral, 6500 K is the blue-grey of an overcast sky — the same D65 white your monitor is probably calibrated against. We convert kelvin to RGB with the standard blackbody approximation, the same curve camera white-balance uses, so the presets here line up with the numbers on real bulb boxes.

Kept honest

The screen stays awake while the panel is lit wherever the Wake Lock API exists (Chrome, Edge, Safari 16.4+) — the status line above says when it's holding. On iPhone Safari, true fullscreen isn't allowed for web pages, so the panel fills the viewport; installed to the home screen, it goes edge-to-edge. Your link button encodes the exact temperature and dim, so ?k=3200 reopens tomorrow's light today.