What are the advantages of mobile phone autofocus?

Simply put, focusing is to change the distance between the lens and the photosensitive element, so that the object in a specific position passes through the imaging focus of the lens and falls right on the photosensitive element to get the clearest image. The parallel light from infinity will fall on the focal length of the lens through the lens, so the general pan-focus is to focus on infinity, that is, the photosensitive element is placed far away from the focal length of the lens, and the imaging focus of the near object falls behind the photosensitive element, resulting in blurred imaging. By focusing, the distance between the photosensitive element and the lens increases, and clear imaging can be obtained.

The English name of Focus is focus. Generally, digital cameras have various focusing modes, namely, auto-focusing, manual focusing and multiple focusing modes.

Auto focus:

Traditional cameras use a similar visual ranging method to achieve autofocus. The camera emits an infrared ray (or other rays), determines the distance of the subject according to the reflection of the subject, and then adjusts the lens combination according to the measurement result to realize automatic focusing. This automatic focusing method-direct, fast, easy to realize and low cost-sometimes makes mistakes (when there is something else between the camera and the subject, such as glass, or the light is insufficient, automatic focusing cannot be realized), and the accuracy is poor. Today's high-end cameras generally don't use this method. Because the camera actively emits rays, it is called active, and because it is actually only ranging, it is also called non-TTL because it does not judge whether coking is correct through the actual imaging of the lens.

Compared with active autofocus, passive autofocus was developed later, that is, judging whether coking is correct according to the actual imaging of the lens. The basis of judgment is generally contrast detection, and the specific principle is quite complicated. Because this method is realized by lens imaging, it is called TTL autofocus. It is precisely because this autofocus method is based on lens imaging, which has high focusing accuracy and low error rate, but the technology is complex, the speed is slow (except for the advanced autofocus lens using ultrasonic motor) and the cost is high.

Manual focusing:

Manual focusing, that is, manually turning the focusing ring to adjust the camera lens, so as to make the captured photos clear, largely depends on the judgment of the human eye on the image on the focusing screen, the photographer's proficiency and even the photographer's vision. Early SLR cameras and paraxial cameras basically used manual focusing to complete the focusing operation. Now quasi-professional and professional digital cameras, as well as SLR digital cameras, are equipped with manual focusing function to meet different shooting needs.

Multi-focus:

Many digital cameras have multi-focus function or area focus function. When the focus center is not set in the center of the picture, multi-point focus or multiple focus can be used. In addition to setting the focus position, you can also set the focus range, allowing users to take photos with different effects. Common multi-point focusing includes 5: 00, 7: 00 and 9: 00.

Holographic autofocus

Holographic AF is a unique function of Sony digital camera and a brand-new autofocus optical system. It adopts advanced laser holography technology and uses laser spot to detect the edge of the object, so it can take accurate focused photos even in dark environment, and the effective shooting distance is 4.5 meters.