Aspects of Camera Lenses: Posterior Pole
Camera lenses are complex and precise instruments that project an image onto a photographic medium. We may refer to our individual camera lenses in the singular form, but in reality these lenses are actually compound lenses, which means that they are composed of a few lenses that make up the final image when combined. The lens that is furthest from the camera body and closest to the subject is the anterior lens. The lens that is closest to the camera body but farthest from the subject is the posterior lens.
The posterior lens is the very last lens that light passes through as it is projected onto the image sensor or film. The posterior pole refers to the absolute center of this lens. The axis of the lens begins at the anterior pole, the center of the outer most lens, and ends its run at the posterior pole.
Origin of the Names
Anterior and posterior are names that come from biology. Anterior refers to what is closest to the surface, like the anterior lens is the first layer in your camera's lenses. Posterior surface refers to what is facing the posterior of the body. In this case, it is the last lens that is closest to the camera body.