What is the focus adjustment of traditional cameras? What are the concepts of focal length and telephoto? Are they far and near?

Category: Culture/Art >> Calligraphy and Painting Art

Analysis:

Focus-this is an act to ensure that the image is clear. That is, after removing the camera itself, a clear picture can be obtained by precise focusing. Focusing can generally be divided into manual and automatic.

Focal length-the distance between a point in a curved mirror or lens and its main focus. The curved mirror is counted from its vertex, the thin lens is counted from its center, and the thick lens and lens group are counted from the main plane on the side where its main focus is located.

The focal length of a photographic lens determines the viewing angle and depth of field. To put it simply: the viewing angle and depth of field of a long focal length lens are relatively small, and it can be shot from a long distance or at the same distance; The short focal length lens has a wide viewing angle and depth of field, and can shoot a large scene at the same distance.

Photographic lenses are made into long focal length lenses, medium focal length lenses, standard lenses, wide-angle lenses and ultra-wide-angle lenses (fisheye lenses) as required. For cameras with different frames, due to different frame sizes, the corresponding parameters of long, medium and short focal lengths are also different. As far as the 135 camera is concerned, the general long focal length refers to the lens above 180MM, which is suitable for shooting scenes that are not easy to get close to, such as wild animals, sports competitions, racing cars, etc., and also suitable for shooting close-ups of relatively close-up scenes; The focal length of the medium focus lens is generally 100 ~ 150 mm, which is suitable for shooting portraits or portraits. A lens with a focal length of 45 ~ 60 mm (120 camera is generally 65 ~ 80 mm) is used to being called a standard lens because its viewing angle is close to the human eye, so it becomes the most commonly used lens. A lens with a focal length less than 30MM is called a wide-angle lens, which can shoot a wide range of scenes in a short distance, such as a group of about ten people in a 3×4M room.