A Wallpaper for the Monitor Turned on Its Side
A rotated screen keeps only a narrow strip of a landscape photo, so the picture has to be chosen for its height rather than its width.
Turn a 27-inch 1440p monitor ninety degrees and it becomes 1440 pixels wide and 2560 tall, a 9:16 column that suits long code files and documents. The wallpaper does not rotate with it. A 16:9 landscape image filled into this shape keeps only about a third of its width, the middle strip, and everything that sat left and right of centre is cut away.
That strip rarely holds the reason you liked the photo. A horizon shrinks to a thin band, a sunset loses its sun to the cropped edge, and a wide valley becomes a slice of grass and sky. What survives are subjects that were already tall: a waterfall dropping the full height of the frame, a tower read from base to spire, a single trunk, a narrow street between buildings. A portrait source at least 1440 pixels wide and 2560 tall fills the column without any upscaling.
Windows and macOS both let each display carry its own image, so the vertical screen does not have to share the landscape screen's wallpaper, and spanning one picture across a horizontal and a vertical monitor usually leaves an awkward step at the join. It also helps to notice where the eye rests. The top of a rotated screen sits higher than usual, often above eye level, so the calm part of the image, sky or mist or plain water, belongs up there, with the detail lower down, closer to where your gaze already is.
