What is the focal plane in photography?

The "focal plane" in photography is the plane where the photosensitive film or photosensitive sensor CCD (or CMOS) is located. Theoretically, parallel light (or light from an infinitely distant scene) is focused on the focus by a convex lens.

The focal plane is the surface formed by the main focal point and all sub-focal points of the lens. In a small range around the main focus, the focal plane is a plane perpendicular to the main optical axis through the main focus. Because the lens has two main focuses, there are corresponding focal planes, the first focal plane passes through the front main focus and the second focal plane passes through the back main focus. In a camera, when the object distance is infinite, the second focal plane is the imaging plane.

The most common situation is to shoot with a half shutter and recomposition, such as focusing with a medium focus and half pressing the shutter. However, when changing the camera angle during recomposition, the focal plane will change, and the original clear point may be out of focus. It is especially common in entry-level digital SLR cameras with only 9 or 13 autofocus points.

Many novices like to blur the cream background with large aperture and shallow depth of field when shooting portraits, but too much will also cause blurring. For example, the telephoto lens of f/2.8 is close to the subject, and the depth of field will be very shallow. At this time, the eyes of the subject are in focus, but the nose, ears or other parts of the head are not in the focal plane. Unless, of course, you deliberately create this effect.