What is a nodal point and why is it important in panoramic photography?
Nodal points are sometimes confused in panoramic photography and what we really should be talking about is the “no parallax point”. In simple terms this is the point about which the light coming into the lens is reversed before it moves on to hit the sensor, this is not actually the nodal point but the system’s entrance pupil. The key thing we want to avoid in panoramic photography is parallax error.
Ok so what is parallax error?
Parallax is the movement of foreground objects relative to the background and for panoramic photography there is a fundamental problem when shooting images adjacent to each other with a camera on a standard tripod, as this results in parallax errors. This is easily demonstrated by holding your thumb out at arms’ length. As if the tripod was your neck and your eyeball the camera lens, close one eye, and while focused on your thumb rotate your head back and forth. You will see your thumb magically move back and forward while the background stays relatively stationary – this is parallax. Eliminating parallax is “essential” for the “seamless” stitching of images, so as to give the illusion the final image was created in a single shot. Stitching together images with any parallax at all will result in poor stitch lines, banding and blurred portions of the image. To avoid these problems we use a specialist panoramic head which rotates the camera about it’s no parallax point.