This poem's title, "In an Artist's Studio," immediately places readers in a specific setting: a painter's studio. The first lines make that setting feel both strange and intense. In this whole studio, there's only "One face" in any of the paintings. This artist, it seems, is a man obsessed with one single subject, one model.
The speaker seems as struck by this discovery as the reader might be. The first two lines here insist on the artist's obsession through repetition:
One face looks out from all his canvases,
One selfsame figure sits or walks or leans:
Here, anaphora on the word "one" and parallelism between these lines makes the poem reflect what it describes. These repetitions are a lot like the repetitions between the paintings, which show the "selfsame figure" as she "sits or walks or leans" in various poses. The language here captures this artist's obsessive focus.
A little context about this poem might give the reader an even more vivid picture of this studio. The author, Christina Rossetti, was the sister of a famous Pre-Raphaelite painter, Dante Gabriel Rossetti, who was indeed obsessed with one model: the unfortunate (and gorgeous) Lizzie Siddal. Siddal modeled for Dante Gabriel Rossetti (a dangerous profession for a woman in the Victorian era, when modeling was considered next door to prostitution), waited around for 10 years for him to keep his promise to marry her, and then promptly died of a laudanum overdose.
While this poem isn't explicitly about the relationship between Rossetti, her brother, and his model, a lot of the detail here hints that Rossetti has this sad story in mind—and that perhaps she, as a woman artist, feels a certain kinship with the artist's model. This will be a poem about the way male artistic ideals can trample on women's humanity.