What do optical zoom and digital zoom of digital cameras do respectively?

Analysis:

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 a digital camera is similar to that of a traditional 35mm camera, that is, the scene to be shot is enlarged and reduced by moving the lens. The larger the optical zoom coefficient, the farther the scene is photographed.

Relationship between focal length and viewing angle 1

Relationship between focal length and viewing angle II

When buying a digital camera, many users will ask, what is digital zoom and what is optical zoom? Below, we will use the chart to illustrate.

Optical zoom is achieved by changing the positions 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.

Optical zoom will not lose the picture quality.

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 5-3 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: If a 2-fold zoom lens is fitted on a 4-fold optical zoom digital camera, the optical zoom multiple of this digital camera will be changed from the original 1, 2, 3 and 4 times to 2, 4, 6 and 8 times, that is, the zoom lens multiple is in phase with the optical zoom multiple.

Digital Zoom, also known as digital zoom, is called digital zoom in English. Digital zoom is to enlarge the area of each pixel in the picture through the processor in the digital camera, so as to achieve the purpose of enlargement. This technology is like enlarging the area of a picture with image processing software, but the program is executed in a digital camera. Some pixels on the original CCD image sensor are enlarged by interpolation, and the pixels on the CCD image sensor are enlarged to the whole picture by interpolation algorithm.

(Digital zoom is also achieved through the zoom lever. When the optical zoom reaches the end point, continue to press and hold the zoom lever, and it will automatically enter the digital zoom area. )

Different from optical zoom, digital zoom is the change of the vertical direction of the photosensitive device, which gives people a zoom effect. The smaller the area on the photosensitive device, the user can only see part of the scene visually. However, because the focal length has not changed, the picture quality is worse than normal.

Through digital zoom, the shot scene is enlarged, but its definition will be reduced to some extent, so the practical significance of digital zoom is not great. However, Sony's original "intelligent digital zoom" is said to be an advanced technology that can keep the image clear after digital zoom.

The total zoom number of a digital camera is calculated as follows: For example, the optical zoom of Sony F7 17 is 5 times, while the digital zoom is 2 times, so the maximum zoom number is 10 times. Digital zoom in digital cameras can usually be turned off. In addition, there is a brand-new and unique Sony intelligent zoom function, which can enlarge the zoom shooting without enlarging the particles, so that the enlarged image can maintain the original detail quality. Intelligent zoom provides different degrees of enhanced zoom function according to the choice of different image sizes. Unlike digital zoom, smart zoom can maintain the same image quality as the original image.

At present, the digital zoom of digital cameras is generally about 6 times, and the digital zoom of cameras is about 44 times to 600 times. In actual use, 40 times is enough. Because too large digital zoom will seriously damage the image, and sometimes even because the magnification is too high, it is impossible to distinguish the shot picture. If the 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.