How does Edgar Allan Poe use imagery in The Purloined Letter?

In terms of imagery, Dupin keeps the room dark to consider the Prefect's problem, we can assume that his reasons are that darkness dims the sight and the ears are rendered more acute. In darkness, Dupin is able to listen without examining the Prefect with his eyes. As well, it places more stress on the images in the mind without clouding his thoughts with physical images. Dupin is heightening the senses he needs by eliminating those he does not need.