What does focal length mean? The relationship between focal length and shooting distance.

The longer the focal length, the closer the shooting distance, the brighter the aperture and the stronger the blur effect.

Background blur is a popular and frequently used phenomenon in photography, which is closely related to the focal length of the lens used, the brightness (aperture value) of the aperture 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.

Just determine the focal length of the lens when shooting, 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.

Extended data

Precautions for shooting

1, which is less than the nearest shooting distance of the lens used in shooting, so shooting cannot be done.

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.

The relationship between focal length, shooting distance, aperture value and blur can be calculated. 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.

Canon-Understand the relationship among focal length, shooting distance and aperture.