What is the relationship between focal length, shooting distance and aperture? Help the gods.

The way to understand the relationship among focal length, shooting distance and aperture is as follows: the longer the focal length, the closer the shooting distance and the brighter the aperture, the stronger the blur effect. Understanding the theory of blur can make people take better portrait photos. The popular and frequently used background blur is closely related to the focal length of the lens used, the brightness of the aperture (aperture value) and the shooting distance (the distance from the camera to the subject). The longer the focal length is, the easier it is to blur the background when the aperture value of the lens is constant. Of course, if the focal length is the same, the brighter the aperture, the easier it is to produce blur effect. In addition, the degree of background blur will change with the change of shooting distance. The shorter the shooting distance, the closer it is to shooting, and the greater the blur effect. Therefore, if you want to get a sharp blur effect, you should choose a lens with shorter shooting distance, brighter aperture and longer focal length. Only when taking portrait photography, first determine the focal length of the lens, and then fix the shooting distance after the composition is completed. Therefore, while mastering the basic principle of blur, we also need to master the relationship between lens focal length and shooting distance. Master the focal length and shooting distance in portrait photography, and actually measure the shooting distance of five representative compositions. The shooting distance is 1, which is less than the nearest shooting distance of the lens used in shooting, so it is impossible to shoot. 2. Shoot with a 35mm full-frame camera. Parentheses indicate the lens focal length required for shooting with APS-C camera under the same conditions. Grasp the relationship between focal length and shooting distance with numerical value, and use it flexibly in shooting scenes. The relationship between the size of the subject in the photo and the shooting distance is shown in the above table. The longer the focal length, the longer the shooting distance, so as to keep the size of the subject on the screen unchanged. If the height of the subject is 167 cm, if you want to take a close-up above the chest, the shooting distance with 16mm lens is so short that you almost touch people, while the distance with 200mm lens must be more than 3 meters. If you can remember this value to a certain extent, it is easy to grasp what kind of focal length lens should be used to shoot the scene. Especially when shooting indoors, it is impossible to keep a certain shooting distance from the model in most cases. If you want to take a full-length photo, it is almost impossible to use a lens with a focal length of more than 200mm unless it is such a wide place as a gymnasium. Grasp the approximate relationship between lens focal length and shooting distance, and you won't hesitate when choosing a lens. Observe the real shot image and grasp the different blur effects caused by focal length, shooting distance and aperture value (aperture brightness). The change of blur effect when the focal length of the lens is 16mm and the shooting distance is 50 cm (shot with a 35mm full-frame camera). Even a wide-angle lens that is considered to be difficult to blur will produce a certain background blur effect when the aperture is large enough, the shooting distance is close, and the subject and the background are far apart. But at the maximum aperture, there is already a certain depth of field. When the aperture is around F4, the background is already clear. Judging from the effect of the picture, you can still feel a certain blur effect until F5.6, and the image taken with a smaller aperture is similar to the pan-focus effect. If the background is closer to the subject, the fuzzy aperture value will be smaller at first, and it may be difficult to capture the fuzzy effect around F4. The change of blur effect when the focal length of the lens is 35mm and the shooting distance is 85cm (shot with a 35mm full-frame camera). After the focal length is 35mm, although it is still a wide-angle lens, the depth of field is still much smaller. The blur effect when the aperture is F2.8 is greater than that when the aperture is 16mm. The blur felt from the legend is similar to the blur effect between F4 and F5.6 when shooting with a 50mm lens. Compared with 16mm lens, the visual angle has changed, and the blur effect is similar to that of 50mm lens, but the impression of the photo is slightly different due to different visual angles. When the focal length of the lens is 50mm and the shooting distance is 1.25m, the blur effect changes (shooting with a 35mm full-frame camera). When the focal length is increased to 50mm, the blur degree is further enhanced, which is obviously different from the imaging atmosphere of 16mm and 35mm lenses. The biggest change is that when the aperture is reduced, even if the aperture is reduced to F22, the depth of field is still so small that the background always has no pan-focus effect. It is difficult to blur the background by using a wide-angle lens, and it is difficult to shoot a pan-focus effect by using a lens with a focal length of more than 50 mm Photographers should understand the differences in lens characteristics and use the appropriate lens in appropriate occasions in order to naturally exert their respective performances. The change of blur effect when the focal length of the lens is 85mm and the shooting distance is 1.95 m (shot with a 35mm full-frame camera). 85mm is already in the field of telephoto lens, and the imaging is very different from that of 50mm lens. It's as if there is an invisible dividing line separating the two. The depth of field is small. At F2.8, the front part of the hair was blurred, and the arm was obviously blurred. When using a 50mm lens, the fluffy part in front of the neck and hair is within the depth of field, which is obviously very different. When the focal length of the lens is 135mm and the shooting distance is 2.85 m, the blur effect (shot with a 35mm full-frame camera) is similar to that of an 85mm lens, but the viewing angle is narrowed, so the photos give people a somewhat different impression. The shooting distance is longer and it is easier to control the focus than when using an 85mm lens. Although this shooting distance is not enough to focus on the whole face, compared with the 85mm lens, the focus control is not so strict. The blur size looks bigger, and the blur effect also has the unique atmosphere of telephoto lens. The separation between subject and background is clearer, which makes the whole subject stand out in the picture. The change of blur effect when the focal length of the lens is 200mm and the shooting distance is 4 meters (shot with a 35mm full-frame camera). When the focal length of the lens is 200mm, in fact, it is the focal length of the lens that plays a major role in blurring. When the aperture is reduced from F2.8 to F4, the blur effect is not as obvious as when using lenses with other focal lengths. Even if the aperture is reduced to F22, it is impossible to take a pan-focus photo with overall focus. The shooting distance is correspondingly longer, so not only the face, but also the whole body of the subject is in the same focal plane. That is, shooting with F2.8, all parts of the body are in focus. There is no difference in the focus position of different parts of the face. Whether focusing on eyelashes or nose, the focal plane is almost the same. The real shooting test proves the correctness of the data, and the photographer should also pay attention to the relationship between background distance and color focal length, shooting distance, aperture value and blur. But in fact, we will find that the shape and color of the background will also affect the impression of the whole photo, so this is also a complicated problem. In addition, the distance between the subject and the background is also related to blurring. If you want to blur the background, you should use a lens with long focal length and large aperture as much as possible, and you should also carefully choose the color and shape of the background. In order to enhance the blur atmosphere, we can try to add highlights to the blur, which will make the whole photo look brighter and more conducive to the use of blur effect. From the point of view of controlling the focus position, shooting with an aperture several orders of magnitude smaller than the maximum aperture can obtain a greater depth of field and is less likely to fail. However, the aperture value of the lens will have a great influence on blur, so shooting with the aperture value near the maximum aperture is the basic principle to obtain strong blur. The shorter the focal length of the lens, the more easily blur will be directly affected by the aperture value, or even reduce the aperture by one level, which will bring obvious differences when using such a lens. A telephoto lens mainly uses a long focal length to create a blur effect. The 50-85mm focal length lens, which is mostly used to shoot portraits, is essentially based on aperture value. Use 35mm Quan Huafu model to shoot at F2.8 (shooting distance is 1.5m) and use APS-C model to shoot at F2.8 (shooting distance is 2. 15m). The imaging of APS-C model is like intercepting the central part of the image taken by 35mm Quan Huafu model. In the two legends, the photo on the left was taken with a 35mm full-frame camera, 100mm lens and the maximum aperture F2.8 If you shoot from the same position with an APS-C camera under the same conditions, you can only shoot the part in the red frame. Whether it is Quan Huafu model or APS-C model, blur is caused by the lens, so using the same lens will not change the blur degree. In addition, if you want to shoot the same image range with a 100mm lens as a 35mm full-frame camera, you must shoot farther away from the subject under the same shooting settings. At this time, the shooting distance becomes longer, which will lead to less blur (as shown in the right picture). If the shooting distance is the same, you need to use a lens with a shorter focal length, which will still lead to less blur. View original post >>