Aspects of Camera Lenses: Axis
Camera lenses are extremely complex pieces of machinery that project an image onto a photographic medium, such as an image sensor or film. This is accomplished by the science of optics. One concept to understand about lenses is the axis. When someone refers to the axis of a lens, they are talking about an imaginary line that is drawn from the geometric center of the lens to the photographic medium.
How the Lens Axis Works
Most camera lenses for cameras are actually made of up a combination of multiple lenses. These are called compound lenses. When you use these lenses, light enters the first lens axis, and then travels through the rest of the axis' until it reaches the photographic medium. The axis remains straight throughout the entire journey through the lens. The lens axis enters the lens at a 90 degree angle. Thus, it is perpendicular to the lens' glass.
How Lens Axis Affects Your Photographs
Lens Axis directly determines the perspective of your photograph. The position of your lens axis to your subject will determine the angle of the photograph. The camera should always be positioned with the lens axis viewed as the dead center for the position of the frame.