Why is the SLR mounted on a tripod and the anti-shake turned off?

The anti-shake mechanism of lens is to detect the abnormal movement of lens through electronic gyroscope, and restore the normal path of optical path by adjusting the floating lens in lens group.

After the camera is fixed on the tripod, it will inevitably bring some influence due to the vibration of the reflector, the pressing of the shutter and the careless touch. Under the constraint of tripod, these vibrations are smaller and more frequent than those of human hands due to physiological reasons, which are difficult to be absorbed and digested by anti-shake mechanism, and even produce superposition, bringing the opposite effect.

Therefore, when shooting with a tripod, it is best to turn off the anti-shake function of the lens to avoid possible loss of image quality.

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". So far, anti-shake is divided into three types: optical anti-shake, electronic anti-shake and CCD anti-shake.

Anti-shake type

At present, digital camera manufacturers with optical anti-shake function include Canon, Nikon, Olympus, Konica Minolta, Panasonic and Sigma. There are many ways to realize the anti-shake function. There is only one kind of optical anti-shake in traditional photographic equipment, and digital anti-shake function has also been developed in digital photographic equipment.

1, optical image stabilization

As an optical anti-shake technology? [ 1]? It is not to make the camera body not shake, but to rely on the structure of special lens or CCD photosensitive element to minimize the image instability caused by shake during the use of the operator. Canon and Nikon are the main representatives of anti-shake through lens group. They rely on magnetic force to wrap the suspension lens, thus effectively overcoming the image blur caused by camera vibration, which is more obvious for digital cameras with large zoom lenses.

Usually, when the gyroscope in the lens detects tiny movement, it will send a signal to the microprocessor to calculate the displacement that needs to be compensated immediately, and then compensate the lens group according to the shaking direction and displacement of the lens, thus effectively overcoming the image blur caused by camera vibration. At present, only Konica Minolta can achieve anti-shake through CCD. Its principle is contrary to the optical anti-shake technology of Canon and Panasonic, and it relies on the floating of CCD to achieve the purpose of anti-shake. The principle is that the CCD is fixed on a bracket that can move up, down, left and right, and the direction and amplitude of camera jitter are sensed by the gyroscope, and then the sensor sends these data to the processor for screening and amplification, and the CCD movement amount that can offset the jitter is calculated.

Optical image stabilization includes lens image stabilization and imaging device image stabilization.

Lens anti-shake

Lens anti-shake is to set a special anti-shake compensation lens group in the lens. According to the direction and degree of camera shake, the compensation lens group adjusts its position and angle accordingly to keep the optical path stable. The most famous are Canon EF IS series lenses and Nikon VR series lenses. Recently, Sigma has also successfully developed OS series lenses. These lenses can be used not only in film cameras, but also in DSLR. On ordinary civil digital cameras, some models have adopted optical anti-shake function since 2000. I believe that Olympus Camedia C-2 100UZ and Canon Powershot Pro90 IS, two classic models that were all the rage in those days, still make many digital movie friends with a fever history of more than 4 years remember them vividly.

image stabilization

Anti-shake of imaging equipment is to change the position or angle of imaging equipment after sensing camera shake to keep the image stable. This anti-shake technology is used by Minolta's new DiMAGE A 1 and A2. This technology is almost impossible in the era of film cameras, because moving film is simply an impossible task! It is much easier to move the CCD.

The camera with three CCD color separation imaging can realize the anti-shake function by adjusting the angle of the color separation prism, which should also belong to the anti-shake of imaging equipment.

Digital anti-shake is based on camera shake, which is compensated by software calculation in data sampling and image synthesis. At present, this kind of anti-shake function is mostly used in cameras, but it is rare in digital cameras.

2. Electronic image stabilization

Electronic anti-shake mainly refers to the anti-shake of digital camera by forcibly increasing the photosensitive parameters of CCD, speeding up the shutter speed, analyzing the images obtained on CCD, and then using edge images to compensate. Electronic image stabilization is actually a technology to compensate for jitter by reducing image quality, trying to strike a balance between image quality and image jitter. Compared with optical image stabilization, the cost of this technology is much lower (in fact, it only needs to make some adjustments to the internal software of ordinary digital cameras), and the effect is also poor. At present, Casio and Fuji on the market have adopted electronic anti-shake technology.

3, the fuselage anti-shake

Anti-shake of the fuselage is to design a vibration sensor inside the fuselage, which can analyze the amplitude of hand shake, move the photosensitive element in the opposite direction, offset the influence of hand shake and take a clear image.