What is the geometric center of a photograph referred to as?

The geometric center of a photograph is referred to as the principal point. This term is crucial in photography and photogrammetry because it represents the point where the optical axis of the camera intersects the image plane. The principal point is essential for understanding image geometry and perspective, as it helps in determining the relationship between the camera's position and the subjects being photographed.

In practice, knowing the location of the principal point is important for tasks such as correcting lens distortion and aligning images in photogrammetric applications. It is typically located at the center of the image but can shift depending on how the camera lens is constructed or positioned during image capture.

Other terms in the choices have different meanings: for instance, "central focus" may refer to the area of the image that is most in focus, while "camera axis" refers to an imaginary line through the camera lens pointing outward. "Image origin" is not a commonly used term in this context and could lead to confusion regarding its definition in relation to photographic geometry. Thus, understanding the principal point ensures accurate interpretation and processing of photographic images.