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.
(..) - Bye. Hi, Yvonne. No, he can't hear me. He's too far. He can't hear us, Yvonne. Ok. We'll be home at sharp. Yes, we'll be on time. Bye, Yvonne. - What's up? She's freaking out? - Yeah. It's your surprise birthday again. (..)2011 The Intouchables
(..) Hi. Let's go. Just so you know, he's had a rough night. Just like you, apparently. The day starts at a.m. sharp with the nurse. He needs to hours of care every morning. I'm warning you. Most people give up after a week. (..)2011 The Intouchables