This is the 288th most frequent Korean word.
보였다
"보였다" means "was seen" or "became visible."
In this sentence, '보였다' is used to mean 'was visible,' indicating that the subject (his face) could be seen.
그의 얼굴이 창밖에서 보였다.
His face was visible through the window.
In this usage, '보였다' suggests that details could be observed in the painting, focusing on the perception of details.
그림에서 아주 작은 디테일까지도 보였다.
Even the very small details could be seen in the painting.
Here, '보였다' conveys that something (her glasses) could be seen faintly, emphasizing the condition of visibility.