Joon Ahn is a concept artist based in Los Angeles. He was formerly a concept and background artist at Disney, and is currently the Senior Concept Artist at Riot Games.
As far as I know, he doesn’t have a dedicated website, but does have a portfolio on ArtStation. He also has a blog, but it has not recently been updated.
His ArtStation gallery isn’t extensive, but even so is showcases are variety of approaches in terms of his approach to color, texture and degree of finish.
In many cases his use of light is dramatic and theatrical, in other cases more muted. As is often called for in concept art, his images often evoke a monumental sense of scale.