Board Thread:General Discussion/@comment-36383063-20181111020510/@comment-32271305-20181111021858

The original files are 426 x 568. The more you enlarge them, the more they become blurry (and their quality isn't really great to begin with).

To convert them into HD you'll need to learn how to use a photo-editing software (such as Photoshop, but there are other options) and/or filters that can create that effect, which basically consists in sharping the edges while blurring the rest at the same time.