expression
to the trained eye; if you know what to look for
Fixed expression meaning that someone with expertise or a discerning eye can see what others miss. Often used when pointing out subtle quality, hidden meaning, or skill.
この絵は見る人が見れば、本物だとわかる。
To the trained eye, this painting is clearly genuine.
見る人が見れば、彼の技術の高さがすぐにわかる。
If you know what to look for, you can immediately see the high level of his skill.
A set phrase combining 見る (to see) with the conditional 〜ば form and the generic noun 人, literally 'if a person who sees sees it'. The repetition emphasizes the act of looking with discernment.