Il n’est plus imaginable de ne pas connaitre les règles d’usage concernant les différentes densités de pixels.
L’article Pixel Density, Demystified – How pixel density works and how it affects your designs est le dernier rempart contre l’ignorance.
Mockups for a standard-sized iPhone should be 375×667, not 750×1334 which is the resolution they’re actually displayed at. Most design tools don’t distinguish points from pixels […], so it’s up to designers to pretend that units in pixels are actually points, then have the flexibility to export at two or three times the size.