Purpose of focus ring and zoom ring

The function of the focus ring is to change the distance from the clearest plane to the lens, that is, to adjust the focus ring to ensure that the subject is clear.

The function of the zoom ring is to change the focal length of the lens, that is, adjust the zoom ring to change the perspective of the photo, the size of the subject and the perspective relationship between the subjects.

Depth of field is controlled by three factors: focal length, aperture and the distance between the subject and the lens.

Therefore, the depth of field is controlled by zoom ring, aperture ring and focus ring.

Extended data:

A camera should have three structural systems: imaging, exposure and assistance. The imaging system includes imaging lens, ranging and focusing, framing system, additional lens, filter, effect mirror and so on. Exposure system includes shutter mechanism, aperture mechanism, metering system, flash system, self-timer mechanism, etc. The auxiliary system includes a film winding mechanism, a counting mechanism and a film rewinding mechanism.

Lens is an optical system for imaging, which consists of a series of optical lenses and lens barrels. Each lens has two characteristic data: focal length and relative aperture. The viewfinder is a device for selecting scenery and composition. Everything you can see through the viewfinder can be shot on film.

A rangefinder can measure the distance of a scene, and it is often combined with a viewfinder. Through the linkage mechanism, ranging can be linked with lens focusing and focus can be completed at the same time.