What is the law of axis? What is the triangle principle of lens scheduling?

The so-called axis refers to a virtual straight line formed by the direction of sight, the direction of movement and the relationship between different objects of the subject. In actual shooting, in order to ensure the unity of the correct position and direction of the subject in the TV picture space, the camera should set the position, arrangement angle and scheduling scene within one side of the axis 180 degrees, which is the "axis" that the cameraman must abide by when dealing with lens scheduling. Abiding by the "axis law" is the basic condition to form a sense of unity in screen space and the consistency of visual orientation system. If the position of the camera is always on the same side of the axis during shooting, the movement of the lens is complicated no matter how the pitch of the camera changes. No matter how many shots are taken, the position relationship and moving direction of the subject are always consistent from the picture.

If the camera crosses the original axis and shoots on the other side of the axis, it is called "off-axis". In the picture taken after "off-axis", the position and direction of the subject are different from those in the original picture. Generally speaking, the pictures taken before and after off-axis cannot be synthesized. If hard-wired, visual acceptance will be very confusing.

The lens scheduling on one side of the axis can ensure the unified orientation of human visual direction, subject movement and spatial position in the two-phase composite picture, which is what we call directionality in scene scheduling. Following the axis rule to arrange shooting can ensure that the directionality between pictures is consistent. Although TV photography is a three-dimensional and multi-angle plane modeling art, correctly expressing the direction of objects is the basic requirement for realizing the spatial structure of pictures and the composition of TV pictures. Otherwise, it will confuse the orientation relationship between the subjects on the painting plane, disturb the transmission of the picture content and theme, and even lead to misunderstanding. Take an object that keeps moving continuously and has a certain moving direction as an example. When we change the shooting angle according to the axis rule, the following three directional relationships will occur between two connected lenses:?

(1) With the camera's parallel angle or * * * coaxial angle, the directions of moving objects in the picture will be exactly the same. ?

The so-called * * * coaxial, that is, the shooting angle set by two cameras on the same optical axis, the shooting direction remains unchanged in the connected lenses, only the shooting distance and the scene of the picture change. Due to the wide use of zoom lens, you can also use the zoom of the camera to push and pull, and jointly complete the lens scheduling on the same axis.

(2) On one side of the shaft, there are two opposite positions. The moving objects in the picture are in the same direction, but they are different before and after. In the shooting angle of TV camera, there are two opposite shooting angles: inside and outside. The inside backhand angle is two shooting angles with opposite directions on one side of the axis, and the outside backhand angle is two shooting angles with opposite directions on one side of the axis.

(3) When the optical axis of the lens coincides with the moving direction of the object, there is no change in the left-right direction in the picture, only the distance of the moving object along the optical axis of the lens changes and changes back and forth. In fact, in this case, the optical axis of the camera coincides with the axis, that is, it is located on the line of 180 under the law of axis. The moving subject of this kind of lens scheduling shooting picture has no obvious sense of direction, so it is also called neutral direction. This kind of lens is also called neutral lens. The lens in the neutral direction also conforms to the axis law, and it is often shot at intervals on both sides of the axis, that is, the lens on the original axis and the lens on the rear axis cross and merge into one.