My partner teaches college art classes. Commonly she has students exercise (1) describing the brute surface appearance of a work of art, and then separately, (2) giving an interpretation of what the work "means".
Surprisingly her students have a really hard time focusing on part (1) without slipping into interpretive aspects. In the hope of helping them distinguish the categories, she spends a lot of time working and talking about part (1). But it's a little awkward because neither of us can come up with a concise term-of-art that means that thing.
Example usage: "Please describe this artwork's _______, without giving an interpretation."
(To which a correct answer might be, "This painting is a black square, with a cracked surface, inside a whitish border", while an incorrect answer might be, "The artist is saying that human perceptions and feelings are more important than any concrete objects in the world that may or may not produce them".)
What would be the best word or short phrase for this classification?