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In the process of learning photography, we sometimes hear that the focal length of so-and-so is suitable for shooting so-and-so, such as the ultra-wide-angle lens commonly used by landscape photographers and the 50mm standard lens beloved by portrait photographers.

Why are different camera lens focal lengths suitable for different shooting themes? When choosing a lens, how to find the focus that best suits you?

The influence of focal length mainly affects the angle of view of the photo.

As shown in the picture, shooting the same tree, the long focal angle of view is small, standing in the distance can make the tree fill the whole picture. The view of the short focal length is large and needs to be very close in order to fill the whole picture with the tree.

From this we can see:

The ① distance is constant, the longer the focal length is, the smaller the view range is, and the farther the scene can be photographed.

The ② view range remains the same, and the shorter the focal length, the closer it is to the subject.

Focal length will also affect the virtual degree of the photo (depth of field), other conditions remain the same, long focus can bring greater emptiness.

The focal length will also affect the photo distortion, the barrel distortion caused by the short focal length and the pillow distortion caused by the long focal length. It also depends on the manufacturer's ability to control the distortion. Generally speaking, the distortion caused by the focal length of not less than 20mm can be accepted or even difficult to detect, but no post-correction can be done.

The influence of shooting distance on nearby objects looks large, while distant objects look small. This is an objective perspective law.

As the picture shows, the windows are obviously the same size, but the ones in the distance look smaller. The distance between the windows is the same, but the distance looks smaller.

The previous article mentioned the relationship among view range, focal length and distance. Combined with the relationship between distance and perspective just mentioned, let's give an example.

To take a portrait of a character, the short focal length needs to be very close, the perspective effect is exaggerated, the nose will be very big, the ears will be very small, and the face will protrude outward. Telephoto shooting should stand a little farther, the perspective effect is not strong, the face looks more natural.

After careful observation of the changes in the background, the scene range of the background becomes smaller and stronger in telephoto, making the photo more concise.

Lens focal length and subject lens focal length can be divided into three categories: wide angle, medium focal length and long focal length.

The focal length around the ① 20mm belongs to a wide angle, which is suitable for shooting a wide range of scenes and can take full pictures of the scene. The focal length of the main photo of the 1x mobile phone is between 20 and 30mm, you can feel it.

Landscape photographers will shoot mountains and rivers and galaxies with ultra-wide-angle lenses around 16mm to accommodate the vast scenery of the world.

Landscape photography often needs to add the foreground, the use of wide-angle lens, close to shooting, can enlarge the foreground and obtain a strong sense of spatial perspective.

The lens around the ② 50mm belongs to the mid-focus, which can shoot a picture with a medium angle of view at a medium distance.

It is common in portrait photography to avoid facial deformation caused by being too close, not to be too far away to hinder communication, but also to avoid redundant environmental elements at wide angles.

If the ③ 100mm goes up, it will be telephoto, far away, and have a small view range.

When shooting wild animals, you need to shoot them at a long distance with a telephoto so that they are not disturbed.

The moon is photographed with an equivalent focal length of about 300mm.

In a messy and disorderly place, you can also shoot a very innovative scene through a long-focus small perspective.

Because of the long shooting distance and the weak perspective effect, the mountains seem to be the same size. This is also known as telephoto compression.

Fixed focus and zoom lens

The internal structure of the zoom lens is more complex, so the production cost of the zoom lens is higher than that of the fixed focus lens, and the picture quality is not as good as that of the fixed focus lens.

Although there are wide-angle to long-focal large zoom lenses (such as 20-200mm) that can dominate the world with one lens, photographers still use several small-range zoom lenses (such as a wide-angle to medium-focal 16-35mm and a medium-to long-focal 70-200mm) to improve the quality of the picture.

This article comes from the official account of Wechat: photography Research Society (ID:shoujiPhotography)

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