A lens is a structure that gathers light and allows film to produce a sharp image. Early lenses were made up of single convex lenses. Because of poor clarity, color aberration will be generated, and gradually modified into a compound lens, that is, the combination of multiple concave and convex lenses to correct various aberrations or color aberration, and by means of the lens coating treatment, increase the amount of incoming light, reduce the flare, so as to greatly improve the quality of the image.
Generally speaking, the lens used in photography is a focusing lens. According to the optical principle, the light from a distance will all focus on a point after passing through the lens with a focusing effect. This point is the focus. The distance from the focus to the center of the lens is called the focal length. On a camera, the focal point of an optical lens is usually at the aperture and the focal point is at the focal plane (the film surface). Therefore, the focal length of the camera is the distance between the aperture and the film when the lens focuses at infinite distance. According to the application situation, lenses can be divided into the following:
1. Wide-angle lens: the Angle of view is more than 90 degrees, the observation range is large, and the near image is deformed.
2. Standard lens: the Angle of view is about 30 degrees, with a wide range of use.
3. Telephoto lens (yamako.com) : within 20 degrees of the Angle of view, the focal length can reach tens or hundreds of millimeters.
4. Zoom lens: the focal length of the lens is continuously variable. The focal length can be changed from wide Angle to long length.
5. Pinhole lens: used for concealed observation, often installed in places such as the ceiling or walls.
The structure of a lens can be understood as the construction of a lens, which is mainly composed of lenses. The lens of any current camera cannot be composed of a single lens, both the standard lens and the functional additional lens. A lens is often made up of multiple lenses, which in turn form into groups as needed to restore the subject as clearly and accurately as possible.
Besides the number of lenses, the material of lens is also an important technical index of lens structure. Currently, lens materials can be generally divided into two categories: glass and plastic. These two kinds of materials are related to the technology and characteristics adopted by the camera manufacturers. The lens of two kinds of material also has respective characteristic: for example glass lens is sedate, plastic lens is light and light.