Since Apple released Notebooks with "Retina" Displays that have a very high resolution and the size of UI Elements in Applications and the OS was not the typical size anymore I noticed a strange behavior in Lightroom. I use and 27" 4K Display and use typical 150 %or 125% Scaling in Mac OS so that I can read Icons an text. When I use 100% scaling everything is very small. Lightroom seems to act a little strange. When using OS scaling values between 100% and 200% Lightroom seems to render with 200% regardless of the actual value. You can see that when zooming into images in Lightroom. 200% and 100% zoom in images in Lightroom Classic are not real 100% and 200% anymore. Lightroom seems to expect that the actual resolution of the Display is always 200% of the Scaled version.
I give an Example:
My 27" screen has 3840x2160 pixel. I use 150% Scaling in MacOS. So UI elements have the same size like an 27" screen with 2560x1440 pixels but it still is very sharp due to the good scaling implementation of MacOS. Lightroom seems to render all UI Elements with two times 2560x1440 pixels now. That is 5120x2880. An imported Image in Lightroom with that exact resolution and displayed with a 100% zoom fits the screen exactly. This should not be the case since my screen has only 3840x2160 pixels an with a 100% zoom it should be larger than my screen.
This leads to a performance drawback since Lightroom renders much more than required. Especially when you apply Scale values that are close to 100% but slightly more. 125% for example. On a 4K screen the Rendering is 3008x1692 pixel. Lightroom should still render in 4k but it things that my display has 6016x3384 Pixels. Its laggy and the zoom level are all over the place.
So please implement more than 100% and 200% scaling in MacOS. 125%, 150% and 175% at least. This will increase performance and the Zoom will work as expected. 100% Zoom will be 100%