discerner

/dɪˈsɜrnər/
noun
  1. A person who is able to notice, recognize, or judge things clearly and carefully.
    • He was known as a keen discerner of character, rarely fooled by first impressions.
    • The art critic was a sharp discerner of both beauty and flaws in a painting.
    • As a discerner of talent, she could spot a promising musician within minutes.