Hyperfocal distance explained in detail.

Determine the main plane and focal length: When the incident parallel light (or its extension line) intersects with the emergent convergent light (or its extension line), the main plane of refraction can be determined, and the intersection of this imaginary plane and the optical axis of the lens is the main point. The distance between the main point of the image and the focal plane (focal point) formed by infinite light is called the focal length of the compound lens (strictly speaking, the effective focal length). The same principle can also be used to determine the main surface and focal length of an object. Hyperfocal distance refers to the distance from the center of the lens to the focus, usually in millimeters. The camera lens projects the light in the shooting scene onto the film or sensor. Visible field of view (FOV) is determined by the horizontal and vertical distance of the scene covered by the lens. Large sensors and films have larger FOV and can record more information in the scene. The focal length and FOV are usually based on 35mm film, because this format (35mm) is commonly used.

In 35mm photography, a lens with a focal length of 50mm is called a "standard lens" because the shooting scene is neither enlarged nor reduced, and the shooting range is the same as that seen by the naked eye (the image angle is 46).

hyperfocal distance

Wide-angle lens (short focal length) can make the camera "see wider" because its imaging angle is larger; The telephoto lens (long focal length) can make the camera "see farther", but the visual range is narrower. The following are descriptions of focal lengths corresponding to some typical lenses: By adjusting the hyperfocal distance, photographers can choose to shoot at a shorter distance or a longer distance to get different perspective feelings. Some digital cameras will have barrel distortion at the wide-angle end and pin pad distortion at the telephoto end.

35mm equivalent focal length

Because the sensor of digital camera is smaller than the area of 35mm film, digital camera engineers introduced the concept of "equivalent focal length" to convert the focal length of digital camera lens into an equivalent focal length of 35mm, which is convenient for photographers to study.