a 'sharp' image/picture/photograph [=an image/picture/photograph in which the small details can be clearly seen]
a 'sharp' break from tradition [=a sudden change from the traditional way of doing things]
A 'sharp-eyed' [='perceptive'] reader will notice the book's repeating themes.
(..) Then we are here on common purpose... ...friend. The shards of Narsil. The blade that cut the Ring from Sauron's hand. It's still sharp. But no more than a broken heirloom. Why do you fear the past? You are Isildur's heir,not Isildur himself. You are not bound to his fate. (..)2001 The Lord of the Rings: The Fellowship of the Ring