What are the functions of optical zoom and digital zoom of digital cameras?

Optical zoom relies on optical lens structure to achieve zoom. The zoom mode is similar to that of a 35mm camera, that is, the scene to be shot is enlarged and reduced by the movement of the camera lens. The larger the optical zoom factor, the farther the scene can be shot. At present, the optical zoom magnification of digital cameras is mostly between 2 and 5 times, and the optical zoom effect of some code cameras reaches 10 times. The optical zoom factor of the home camera is 10 -25 times, which can clearly shoot things 70 meters away.

Digital zoom is actually an electronic enlargement of a picture. Some pixels on the original CCD image sensor are enlarged by interpolation. 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. At present, the digital zoom of digital cameras is generally about 3 times, and the digital zoom of cameras is about 44 times to 600 times. In actual use, 40 times is enough.

If the zoom factor is not enough, we can add a magnifying glass in front of the lens. If the shooting angle is small, you can increase the wide-angle lens accordingly. The UV mirror we usually see can be installed in front of the lens to protect the lens from dust.

People who come into contact with digital cameras for the first time often have such confusion. The photos taken are not clear enough, and there will always be ghosting or blurring. The reason is that the shutter speed is too low, except for occasional out-of-focus (that is, the camera can't focus normally). Generally speaking, under the hand-held condition, the shutter speed for taking clear photos should reach the reciprocal of the focal length or even higher. For a simple example, the equivalent focal length of the lens of Canon A75 is 35mm- 105mm, so the shutter speed at the wide-angle end should be kept at least 1/40 seconds to ensure that the photos taken are clearer, while the shutter speed at the telephoto end should reach1125 seconds. And if the lighting conditions at the scene can't meet this requirement, it's not so simple to take clear photos. As you can imagine, for those products with optical zoom of 10 times, anti-shake technology is even more essential, because the telephoto end of these products often reaches more than 370MM, so the shutter speed must be above 1/400 seconds to be qualified, otherwise it can only be worse than sighing.

The concept of anti-shake was first put forward by Nikon Corporation of Japan, and in 1994, a pocket camera with shock absorption (VR) technology was introduced. The following year, Canon of Japan introduced the world's first lens EOS 75 ~ 300mm f/4 ~ 5.6IS with image stabilizer, where IS is the abbreviation of image stabilizer, which is also known as "anti-shake system".

In fact, in actual shooting, the jitter of photographer's hand during film or CCD/CMOS exposure is objective and inevitable. Only a special mechanism can be used to reduce the image blur caused by photographer's hand jitter. So far, anti-shake is divided into three types: optical anti-shake, electronic anti-shake and CCD anti-shake. At present, digital camera manufacturers with optical anti-shake function include Canon, Nikon, Olympus, Konica Minolta, Panasonic and Sigma.