PPI (DPI) is actually bad unit for display's "sharpness", because it makes difficult to comparise different types of devices, meant to be watched from different

PPI (DPI) is actually bad unit for display's "sharpness", because it makes difficult to comparise different types of devices, meant to be watched from different distances. The correct universal unit is pixels-per-arcsecond, i.e. the ratio between PPI and viewing distance, making possible to compare e.g. mobile screen with video projector image.