He theorized on this idea in his 1800 treatise Reflections and Advice to a Student on Painting, Particularly on Landscape, developing a concept of a "landscape portrait" in which the artist paints a landscape directly while looking upon it, taking care to capture its particular details.
In his 1800 book, "Reflections and Advice to a Student on Painting, Particularly on Landscape," he proposed a concept called "landscape portrait." This involved painting a landscape directly while observing it closely, capturing all of its unique features.