What is a shutter? What is the function of shutter?

Shutter is the mechanism used by camera to control the effective exposure time of photosensitive film. It is an important part of the camera, and its structure, form and function are important factors to measure the grade of the camera. Generally speaking, the larger the shutter time range, the better. The camera relies on this device to control the shutter time, thus controlling the amount of light entering the camera.

2. Function

The main function of camera shutter is to control the exposure time. Different exposure time will lead to different results. When shooting, we can shoot different picture effects by controlling the shutter speed, such as curing fast-moving objects with high-speed shutter, shooting light tracks with slow shutter and so on.

Extended data

Classification:

1, mechanical shutter

In a film camera, the shutter is a mechanical rotating mirror. At each exposure, it rotates 360 degrees and alternately closes and opens the film door within a specific time. The rotating speed of the shutter is mechanically fixed, which is determined by the frame rate, and the exposure time is determined by the shutter angle.

2. Rolling shutter

The electronic shutter of many digital cameras is equipped with a rolling shutter, and the data in it is read out column by column from the top to the bottom of the sensor, and then reset to the next picture exposure.

In an image where the shutter is obviously tilted and will become a vertical line, if there is a camera or a subject passing through the picture quickly. If the reading speed of the sensor is particularly slow and there is rapid movement in the picture, unnecessary dynamic overlap will occur and the whole image will be distorted.

Most roller blinds are very fast, which minimizes potential problems. Many RED and Arri cameras have rolling shutters, which are more cinematic than global shutters. Even for high frame rate cameras, such as Phantom digital cinema cameras, the reading time is only 1 millisecond.

3. Global shutter

A global shutter is different from a rolling shutter. At the end of a complete exposure, the light is completely blocked at one time, and then the data is read and reset for the next exposure.

The global shutter keeps vertical lines or objects moving horizontally on the screen. However, the feeling of exercise is obviously different. According to the realization of global shutter, compared with rolling shutter, light and possible dynamic range will only consume a little.

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