optical zoom

The English name of Optical Zoom is Optical Zoom, and digital cameras rely on optical lens structure to achieve zoom. The optical zoom mode of digital camera is similar to the traditional 35mm camera, that is, the lens moves to enlarge and reduce the scene to be shot on CCD or CMOS. The larger the optical zoom coefficient, the farther the scene is photographed.

Optical zoom is achieved by changing the position of lens, object and focus. When the image plane moves in the horizontal direction, as shown below, the visual field and focal length will change, and the farther scenery will become clearer, making people feel that the object is moving forward.

Obviously, there are two ways to change the perspective. One is to change the focal length of the lens. In photography, this is optical zoom. The focal length of the zoom lens is changed by changing the relative position of the lens. The other is to change the size of the imaging plane, that is, the diagonal length of the imaging plane. In today's digital photography, this is called digital zoom. In fact, digital zoom does not change the focal length of the lens, but changes the viewing angle by changing the diagonal of the imaging plane, thus producing an effect equivalent to the focal length change of the lens.

Therefore, we can see that some digital cameras with long lenses have more room for moving the internal lens and photoreceptor, so the zoom factor is also larger. We see that some ultra-thin digital cameras on the market generally have no optical zoom function, because the roots in the fuselage are not allowed to move the photosensitive devices, while Sony F828, Fuji S7000 and other "long lens" digital cameras have optical zoom functions as high as 5 or 6 times.

At present, the optical zoom multiple of digital cameras is mostly between 2 and 5 times, which can zoom objects beyond 10 meter to 5-2 meters; There are also some digital cameras whose optical zoom effect is 10 times. The optical zoom factor of home camcorder is 10 ~22 times, and it can clearly shoot things 70 meters away. Using a magnifying glass can increase the optical zoom factor of the camera. If the optical zoom factor is not enough, we can add a zoom lens in front of the lens. The calculation method is as follows: A 2-fold zoom lens is set on a 4-fold optical zoom digital camera, and then the optical zoom multiple of this digital camera will be changed from the original 1, 2,3,4 times to 2,4,6 times and 8 times, that is, it is obtained by multiplying the zoom lens multiple and the optical zoom multiple.