focal length的意思|示意

【Focal Length: How Cameras Use it to Focus on the Subject】

The focal length of a camera lens refers to the distance from the lens to the point where the light rays converge. This is the point at which the lens focuses on the subject of the photograph. Different lenses have different focal lengths; the most common focal lengths for DSLR lenses range from 18mm to 300mm.

To understand how focal length affects the image, it is important to understand how cameras work. Light enters the camera through the lens, where it is focused on to the camera's sensor. A longer focal length will focus on a smaller area and make the background appear further away. This is known as a “telephoto” effect, and it allows the photographer to capture images with greater depth of field. A shorter focal length, on the other hand, lets the photographer capture a wider view of the subject without the background appearing too far away. This is known as the “wide angle” effect.

The focal length of a lens also has an effect on the apparent size of the subject. A longer focal length will make the subject appear larger, while a shorter lens will make the subject appear smaller. This can be used to create some interesting effects; for example, a wide angle lens can make a person appear much larger than they actually are.

Focal length is an important part of photography and is an aspect that should be considered when selecting a lens for a particular shot. Different lenses have different focal lengths and each lens will have different effects on the image. It is important to understand how the focal length will affect the photograph before taking the shot.