What is defined as the distance measured from the lens to the sensor when focused on a subject at infinity?

The focal length is the correct term for the distance measured from the lens to the sensor when the lens is focused on a subject at infinity. This measurement plays a crucial role in photography and cinematography as it defines the lens's capability to magnify subjects and affect the field of view.

A longer focal length results in a narrower field of view and greater magnification of distant subjects, while a shorter focal length provides a wider angle of view. Understanding focal length helps in choosing the appropriate lens for a specific shot or scene, influencing the resulting composition and perspective.

Depth of field, on the other hand, refers to the range within a photo that appears acceptably sharp, which is influenced by factors such as aperture and focal length but is not defined solely by the distance from the lens to the sensor. Aperture concerns the size of the lens opening that controls the amount of light entering the camera and also impacts depth of field but does not define the distance itself. B-Roll refers to supplemental footage that enhances the primary shots and does not relate to lens measurements at all. Therefore, focal length is specifically identified with the distance from the lens to the sensor when focused on a distant subject.