Testbilder are the X-ray vision of the display world. While a 4K movie is designed to trick your eyes into seeing reality, a test image is designed to show you the wires and scaffolding behind the magic. They reveal that not all 4K panels are created equal, and sometimes, the most beautiful image on your screen isn't a sunset—it’s a perfect checkerboard of grey.
Fine horizontal and vertical lines should be distinct without "flickering" or blurring. Identifies non-functioning sub-pixels. 4k testbilder