One of the first tests I do when unboxing a new iPhone is to compare its display performance to a previous model. 5s vs 5: 5s undoubtedly has better contrast, slightly so. Noticed this on a friend's as well by just looking at cover art briefly. Not only that but color temperature has been made warmer, making colors more accurate. They pop more. I know it's not a new device illusion but I'm always surprised people don't notice the display upgrades unless Apple advertises them. They're small but noticeable.