What is axial photography?

Generally, buildings are standing on the ground. In order to take a complete picture, the camera should be tilted slightly upward. Because the lower part of the building is close to the upper part and far from the upper part, the convergence effect of "the lower part is big and the upper part is small" will be adopted. The lens itself is not deformed, and the reason for this phenomenon is the perspective relationship. Correction: The camera is shooting a building. At this time, the lens angle may be insufficient, and it is necessary to change a lens with a wider angle. For a 35mm camera, the equivalent method is to shoot directly at the target with a lens with the same focal length but a larger viewing angle, and move the film to the reserved position when cutting (actually, the lens translates in the opposite direction). This kind of lens is the "axis-shifting lens", and the principle is as mentioned above. A lens that moves the optical axis to adjust the viewing angle. The function of the shift lens is not only to correct the perspective deformation, but also to adjust the focal plane position. In general, the focal plane of the camera is parallel to the film plane, and the scene in the focal plane is clear and the Jiao Wai is blurred when shooting with large aperture; If the focal plane is adjusted by moving the axis lens, the sharpness can be changed. Obviously, shifting lens is most suitable for architecture, landscape and commercial photography. EF shift lens has no AF function. This kind of lens is designed to be movable because it has a special device that can move or tilt, and its focal length is generally 28mm or 35 mm The axis-shifting lens can be used to correct the perspective problem. When you take a photo, the location is much closer to the bottom of the building than to the top of the building, and the following will happen. The whole building image is compressed, and the roofs are also gathered together, which will cause the building to collapse. This situation can be avoided if a shift lens is used. Shift-axis lens can eliminate perspective distortion, because when shooting tall buildings, the lens needs to be tilted upward to get a panoramic view. Results The film plane is at a certain angle with the main line of the high-rise building, and the upper part becomes smaller due to the long distance between objects, resulting in perspective deformation. After the axis-shifting lens moves, the center of the lens does not pass through the center of the film, so the distance between the upper and lower parts of the film to the center of the lens is not equal. Although the upper object distance is far, the corresponding image distance of the lower part is also far, and the corresponding magnification change offsets the perspective deformation. As long as the film plane is parallel to the main line of the building, there is no perspective deformation in the photos taken. It is equivalent to shooting with a large camera (such as 120 camera) with the same focal length lens (wider angle) and then cropping to 135 frames. If we shoot with a super wide-angle lens and then enlarge it, the effect is the same as that of a shift-axis lens, but the resolution cannot be fully utilized. Depth of field control not only requires the lens to have the function of shifting axis, but also requires the lens to have the function of swinging, such as Canon TS-E lens. As can be seen from the figure, there is an arc and scale, and there is a small plane near the axis of rotation, all of which serve the rotation function. By shifting the axis and swinging, an inclined plane can be focused on the focal plane, so that the object on the inclined plane can be imaged clearly. This can't be done on a normal lens. Ordinary lenses can only focus clearly on the plane perpendicular to the lens axis. These functions of the axis shift lens are only available in large landlines. To achieve these functions, not only complex mechanical structure is needed, but also the lens has a larger field of vision and a larger rear working space, so the axis-shifting lens is very expensive. Due to the special mechanical structure, the axis-shifting lens generally has no automatic aperture. The main feature of axis-shifting camera lens is that the main optical axis of the whole camera lens can be translated, tilted or rotated on the premise that the plane position of the camera body and the film remains unchanged, so as to adjust the perspective relationship of the shot image or focus the whole area. The reference clear image field of the camera lens with shifting axis is much larger, which is to ensure that the camera lens can still get a clear image after its optical axis is translated, tilted or rotated. Axis-shifting photographic lens is also called "TS" lens ("TS" is English "Tilt &；; The abbreviation of "shift", namely "oblique shift"), "oblique beat", "shift beat" and so on. After the 35mm single-lens reflex camera adopts the shifting camera lens, the single-lens reflex camera also has the function of controlling the viewing angle by adjusting the leather cavity of the large-scale combined camera, thus expanding the application range of the 35mm single-lens reflex camera. In the field of professional photography, the lens of shifting axis camera plays a considerable role. The shift-axis camera lens has two main functions: 1. Is to correct the perspective deformation of the subject; 2. It is to focus on the whole area of the subject, so that the far and near subjects in the picture form a clear image. Axis-shifting lens is widely used in architectural photography. When shooting the shape of a building, a camera lens with wide-angle focal length is often used. However, due to the perspective effect of wide-angle lens, the lines of architectural modeling converge upward. When shooting architectural modeling with a shift camera lens, this line convergence phenomenon can be corrected by the angle adjustment function of the lens, so that the building in the picture does not have the usual inclination or even looks like it has been pushed down, but it still looks very vertical. Shift-axis photographic lenses are also often used to take pictures in which all areas are in focus. In commercial photography, the translation and tilt shooting functions of this lens are often used in combination, which can correct the perspective deformation of the subject and obtain a full-area focusing effect that is difficult to achieve with ordinary photographic lenses.