Using an external display is generally limited to connecting your Mac to it and selecting the desired definition in System Preferences. Except with screens in a format that is a little out of the ordinary, it sometimes happens that we do not find the right fit, especially with Apple Silicon Macs which manage fewer different definitions.
The first thing to try in this case is, still in the display settings of the Monitors panel, to click on the “To scale” option while holding the Option (⌥) key. This unlocks additional definitions.
If despite this you still cannot find a suitable definition, try BetterDummy. This free and open source application was created by Istvan Toth, one of the developers of the excellent MonitorControl. He designed it specifically for Apple Silicon Macs (although it works in part with Intel Macs) with which he could not select a resolution suitable for him for a Lenovo 24 “QHD external display (2560 × 1440 pixels).
BetterDummy uses a trick to unleash the possibilities: the utility creates a virtual screen which then allows you to apply to the external screen, or even the internal screen, all kinds of different definitions. For example, you can select a “Retina” definition of 1920 × 1080 on a QHD screen.
There are several steps you need to take to benefit from BetterDummy. In the application menu, you must start by creating a virtual screen (a « dummy »). This must correspond to the ratio of the screen whose definition you want to modify. In the following example, I am using a 16: 9 Dummy.
Once it’s done, go to System Preferences > Monitors. You will then see a new screen. Click on “Display Settings”, select the 16: 9 Dummy screen and choose the following options:
- Use as: “Copy for … (the screen whose definition you want to modify)”
- Optimized for: Dummy 16: 9
When it’s done, change the “Use as:” option back to “Main screen”.
From there, you can change the definition of the external screen very freely either in System Preferences (click on “To scale” while holding Option) or via BetterDummy in the menu bar.
As this is a new hack, everything is not yet very well established. The choices made in the Monitors panel are not always retained, in this case you have to repeat them until you obtain the equivalent of the above capture. You will quickly see if the change of definition works or not anyway.
I did my tests with version 1.0.13. A version 1.1 which must improve many points is currently in alpha (it’s limited to 10 minutes of use, with the developer wanting it to be used for testing only for now).
BetterDummy bringing a lot of flexibility to the management of the display, it can be used in many cases, such as to use a remote Mac mini to the definition of its choice or to modify the definition of an iPad in Sidecar . Version 1.1 will go even further by notably adding a Picture in Picture mode allowing you to display the virtual screen in a window.
The dons and the contributions are appreciated.
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