Popularize knowledge of photography technology

1, what's the point? What is depth of field?

When shooting, the process of adjusting the camera lens so that the scene at a certain distance from the camera is clearly imaged is called focusing, and the point where the photographed scene is located is called focus.

The scene (close to the camera) within a certain distance before and after focusing is clear, and this clear range before and after focusing is called depth of field. The depth of field is first related to the focal length of the lens: the focal length is long, the depth of field is small, and conversely, the depth of field is large. Secondly, the depth of field is related to the aperture: the smaller the aperture (the larger the aperture value, the smaller the aperture), the greater the depth of field; Conversely, the smaller the depth of field.

2. What is optical zoom? What is digital zoom?

Optical zoom relies on the structure of the optical lens to achieve zooming, that is, the shot scene is enlarged and reduced by the movement of the lens group in the lens, which is a kind of "true magnification".

Theoretically speaking, the larger the zoom factor, the lower the lens imaging quality and the easier it is to shake, so it is necessary to balance the imaging quality and zoom factor according to the actual needs. In fact, digital zoom enlarges the picture through interpolation algorithm, which can reach countless times in theory, but the imaging quality is also poor.

3. What is "CCD"?

CCD is the abbreviation of charge coupled device, which was first developed by Bell Laboratories in 1969. It can convert incident light into electric charge, store it, transfer it, and convert the imaged optical signal into electric signal for output. It has photoelectric signal conversion function and is an ideal camera element. Its main features are good sensitivity, less noise and fine imaging, but it is slow and consumes a lot of electricity.

4. What is CMOS?

CMOS, translated as "complementary metal oxide semiconductor" in Chinese, is actually a general semiconductor material, which is widely used in the manufacture of computer chips. In the field of camera shooting or photography, CMOS refers to the photosensitive chip made of this material. Its basic principle is similar to CCD, but it is somewhat different. Its biggest characteristics are high speed, high integration and power saving. Early CMOS was noisy, and the imaging quality was difficult to compare with CCD. However, in recent years, new CMOS technologies represented by Sony and Canon have greatly improved while maintaining their original advantages, and they have more cost advantages in terms of large size.

5. What is the difference between optical image stabilization and electronic image stabilization?

Optical anti-shake system can realize shock absorption and anti-shake by changing the position of lens group or photosensitive chip. Its anti-shake effect is better than electronic anti-shake, but its disadvantages are high cost, power consumption and space requirement. Therefore, it is generally used for large high-end cameras with high lens magnification and strict requirements on image quality.

Electronic anti-shake system refers to the anti-shake function realized by circuit pixels and adjusted by built-in sensors. In short, jitter, whether up, down, left or right, can be corrected by total pixels. Ordinary cameras are equipped with electronic anti-shake system.

6. What is an aperture?

Aperture is a retractable structure inside the lens, which is used to control the amount of light. Aperture and shutter are the main means to control the whole image. The aperture size is expressed by f value. The smaller the aperture value, the larger the aperture, and the more light passes through the lens. The complete aperture values are as follows: 1,1.4,2.8,4,5.6,8, 1 1,16,22,32,44,64. The amount of light entering the upper layer is twice that of the lower layer.