Inside Lumendial: Brightness for Every Screen on the Desk
Lumendial is a small Mac utility from 1dot1 that puts a brightness slider for every connected display in the menu bar. The Mac's own screen and each external monitor sit in one panel, side by side, with presets, keyboard shortcuts and an evening schedule around them. This teardown walks through it screen by screen and explains the decisions behind each part.
The problem it answers is familiar to anyone with a second screen. The brightness keys on a Mac change the built-in display and usually leave the monitor on the desk exactly as it was, so the evening ends with one screen comfortably dim and the other glaring. Changing the monitor means reaching round the back for small buttons and a menu that was never designed to be used every day. Lumendial moves that control to the same place as the clock and the battery.
One slider for each screen
Clicking the menu bar icon, a monitor with a sun on its screen, opens a panel that lists every connected display. Each one is named the way macOS names it, so a laptop shows up as Built-in Retina Display and a monitor under its own model name, and each has a slider with its level as a percentage beside it.
Above them sits All displays, which moves every screen together. The two kinds of slider cover the two things people actually do: balance one screen against another once, when a monitor is plugged in, and then turn everything up or down together as the light in the room changes. Keeping both in view means there is no mode to switch between.
Each display row also carries a small badge, Built-in, DDC or Software dim, that says how that screen is being controlled. It is a small detail, but it answers the first question anyone asks when a monitor behaves differently from the laptop.
The Mac's screen and the monitor's own backlight
The built-in screen, and Apple displays, are set through the same system brightness service that the brightness keys use. Nothing is simulated: the slider and the keys move the same setting, and either one can be used.
External monitors are different. Most accept brightness and contrast commands over the video cable through a standard called DDC/CI. Lumendial checks each monitor when it is connected, and if the monitor answers, its slider drives the real backlight. That matters for comfort and for image quality: a lower backlight actually emits less light, rather than only darkening the picture. Monitors that answer also get a smaller contrast slider under the brightness one.
Monitors take a moment to apply each command, so while a slider is being dragged only the latest value is sent. The monitor may change in small steps rather than perfectly smoothly, but it never falls behind a queue of stale commands.
When a monitor does not answer
DDC is not guaranteed, and it is worth saying so plainly. Whether it works depends on the monitor, the cable, and any dock or adapter in between. Some monitors ship with DDC/CI switched off in their own on-screen menu. Most TVs never answer. HDMI on some Macs, and some docks and adapters, do not pass the commands through at all.
A monitor that stays silent is not left out. It gets the Software dim badge and is dimmed by scaling its colour output, the display's gamma, instead of its backlight. Because this happens at the display output, screenshots and screen recordings are not darkened.
Software dimming is the kind of change that must never outlive the app, so Lumendial puts normal colours back whenever it quits. If it ever stops unexpectedly, it restores them at the next launch, and logging out and back in does the same. Night Shift and colour profiles keep working underneath, and return exactly as they were once the slider is back at 100%. If macOS reports a display's level but refuses changes, the slider is shown greyed out rather than pretending to work.
Day, Evening, Night
Three presets are always there: Day sets every display to 100%, Evening to 60% and Night to 25%. One click moves every screen, and the preset that matches the current level is shown filled in, so the panel also doubles as a quick reading of where things stand.
Any level can become a preset of its own. Save current asks for a name and stores the present level, up to six saved presets, which is enough for a reading setting or a late film without turning the row into a list to scroll. A saved preset is removed with a right-click on its button; the three defaults cannot be deleted, so the basic set is always one click away.
A right-click on the menu bar icon shows the same presets, with Brighter and Dimmer, without opening the panel. For someone who only ever uses two or three levels, that menu is the whole app.
Brighter and dimmer, from anywhere
Control-Option-Up Arrow makes every display brighter, and Control-Option-Down Arrow makes them dimmer, from any app. Each press moves one step of sixteen, so a full sweep from dark to bright takes a moment rather than a long hold.
The menu bar briefly shows the new level next to the icon, then settles back. There is no large overlay in the middle of the screen: the number appears where the eye already goes for status, and disappears without needing to be dismissed. If another app already owns those combinations, the shortcuts simply do nothing, and the sliders and right-click menu still work.
Dims itself in the evening
Dim in the evening is a switch in the panel. Turn it on, use the arrows beside At to pick a time in steps of fifteen minutes, choose the preset to go to, and set a Back to Day time for the morning.
It works from the time of day only. Sunset-based schedules need location, and location is a permission this app has no other reason to ask for, so a plain clock time was the better trade. It is also more predictable: the screens dim at nine because nine was chosen.
Two rules keep it from getting in the way. If the Mac is opened during the evening window, it dims straight away rather than waiting for the next day. And a change made by hand in between is left alone until the next set time, so turning a screen up for a film is not undone a minute later.
Built in black and white
Like the other 1dot1 Mac apps, Lumendial is greyscale in light and dark mode. The icon is a black monitor with a white sun on its screen, and the menu bar glyph repeats it at a smaller size. The panel uses plain rows, thin sliders and outlined preset buttons, with the active preset filled in black, so the only strong mark in the panel is the one that says what is set.
It is a universal app for Apple silicon and Intel Macs, runs on macOS 13 Ventura or later, and asks for no permissions: no Accessibility, no Screen Recording, no location. There is no account, and everything stays on the Mac.
How to use it, feature by feature
The same instructions are in the short guide inside the download.
Installing and opening it the first time
- Unzip the download, drag Lumendial.app into Applications and open it. A monitor-with-a-sun icon appears in the menu bar.
- Lumendial is signed and notarized by Apple, so it opens with a normal double-click.
Changing brightness
- Click the menu bar icon to see every connected display, each with its own slider.
- Drag a display's slider to change just that display; the percentage beside it shows the level.
- Drag All displays at the top to move every display together.
- Click anywhere else, or press Escape, to put the panel away.
How each display is controlled
- Built-in: the Mac screen is set directly, exactly like the brightness keys.
- DDC: a monitor that answers over the cable has its real backlight set, and gets a smaller contrast slider too.
- Software dim: a monitor that does not answer is dimmed by scaling its colour output. Screenshots and recordings stay bright.
- Read-only: if macOS reports a display's level but refuses changes, the slider is greyed out.
Permissions
- None are needed. Lumendial does not ask for Accessibility, Screen Recording, location or anything else.
Presets
- Press Day, Evening or Night to set every display to 100%, 60% or 25%.
- Press Save current, or Save Current as Preset in the ••• menu, and give the level a name. Up to six can be saved.
- To delete a saved preset, right-click its button, or use Delete Preset in the ••• menu. Day, Evening and Night always stay.
- The preset matching the current level is shown filled in.
- Right-click the menu bar icon to choose a preset without opening the panel.
Keyboard shortcuts
- Press Control-Option-Up Arrow for brighter, from any app.
- Press Control-Option-Down Arrow for dimmer.
- Each press moves every display one step of sixteen, and the menu bar shows the new level for a moment.
Dimming in the evening
- Turn on Dim in the evening in the panel.
- Use the arrows beside At to pick the time, in steps of 15 minutes, and choose the preset to go to.
- Use Back to Day at to pick the morning time, when every display returns to Day.
- If the Mac is opened during the evening window it dims straight away; a change made by hand in between is left alone until the next set time.
Making it fit
- Choose Open at Login, in the ••• menu or the right-click menu, to keep Lumendial in the menu bar from startup.
- Choose Quit Lumendial to quit; any software-dimmed display is put back to normal colours first.
If something does not happen
- A monitor shows Software dim instead of DDC: check that DDC/CI is on in the monitor's own menu, try a direct HDMI or DisplayPort cable rather than a dock, then unplug and reconnect it. Some monitors, most TVs and some HDMI ports never answer; software dimming still works on them.
- The monitor changes in steps or lags: monitors take a moment to apply each command, and only the latest value is sent while dragging.
- The shortcuts do nothing: another app already owns Control-Option-Up or Down. Use the sliders or the right-click menu.
- A software-dimmed screen stays dark after a crash: open Lumendial again and it restores normal colours at launch. Logging out and back in does the same.
- Night Shift or a colour profile looks different while dimmed: dimming works on top of the current colours, and they return exactly at 100%.
Get Lumendial
Lumendial is available on 1dot1 as a single download, with the guide, a README and the licence inside the zip.