What is the amount of light entering when the camera stops automatically?

Aperture is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens, usually in the lens. We use the f value to represent the aperture size.

Aperture f value = lens focal length/lens aperture diameter

As can be seen from the above formula, to achieve the same aperture f value, the aperture of a long focal length lens is larger than that of a short focal length lens. The complete series of aperture values is as follows:

f 1，f 1.4，f2，f2.8，f4，f5.6，f8，f 1 1，f 16，f22，f32，f44，f64

It is worth mentioning here that the smaller the f value of the aperture, the more light enters in the same unit time, and the light entering amount of the upper level is exactly twice that of the lower level. For example, if the aperture is adjusted from f8 to f5.6, the amount of light entering will double. We also say that the aperture is enlarged by one level. For consumer digital cameras, the aperture f value is often between f2.8-f 16. In addition, many digital cameras can adjust the aperture by 1/3. The English name of Aperture is aperture. Aperture is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens. It is also an extremely important index parameter of the camera, usually in the lens. Its size determines how much light enters the photosensitive element through the lens. We use the f value to represent the aperture size. Aperture f value = lens focal length/lens aperture diameter According to the above formula, to achieve the same aperture f value, the aperture of a long focal length lens is larger than that of a short focal length lens.

Aperture and shutter take precedence.

In addition to providing automatic mode, advanced digital cameras usually have two options: aperture priority and shutter priority, so that you can decide a certain aperture value or a certain shutter value on some occasions, and then match the appropriate shutter or aperture respectively to present different depth of field (sharpness) or effects.

Aperture priority exposure mode

After we decide the aperture f value ourselves, the camera metering system will automatically choose the appropriate shutter speed (which can be an accurate stepless shutter speed) according to the light conditions at that time. A digital camera with an exposure mode dial usually engraves the letter "A" on the dial to indicate the aperture priority mode (see Figure 4). Aperture prerequisite mode is suitable for photography that emphasizes the depth of field effect.

Because the focal length of digital camera is much shorter than that of traditional camera and the aperture of lens is small, it is difficult to produce narrow depth of field. Some digital cameras have a special portrait exposure mode, using built-in programs to blur the foreground and background. Aperture type

Fixed aperture. The simplest camera only has a fixed aperture with a round hole.

Walter Hauser aperture. The initial variable aperture is just a series of circular holes with different sizes, arranged around a disk with a central axis; Rotating the disc can move the circular hole with appropriate size to the optical axis, thus controlling the aperture. John Vaught Hauser invented this kind of aperture in the middle of19th century.

The cat's eye aperture consists of a metal plate with an oval or diamond hole in the middle, which is divided into two parts. Two metal sheets with semi-elliptical or semi-diamond holes are arranged in opposite rows and moved relative to each other to form a cat's eye aperture. Cat's eye aperture is mostly used for simple cameras.

Iris-shaped aperture is composed of a plurality of overlapping arc-shaped thin metal blades, and the size of the central circular hole can be changed by the clutch of the blades. Some cameras can change the aperture of the diaphragm by rotating the ring on the lens barrel, while others automatically change the aperture of the diaphragm by controlling the micro-motor through the microprocessor chip. There can be as many as eighteen arc-shaped thin metal blades. The more arc-shaped thin metal blades, the closer the aperture is to a circle. By designing the shape of thin metal blades by computer, a nearly circular aperture can be obtained with only 7 thin metal blades. Instantaneous aperture

The aperture of a SLR camera is instantaneous, and only when the shutter is opened will the aperture be reduced to a predetermined size. Usually the aperture is at the maximum position. Double shutter aperture

The aperture of some simple cameras has shutter function. Most of these double shutter apertures are cat's eye apertures with two blades. Different from the simple cat's eye aperture, the double shutter aperture is usually completely closed: at the moment when the shutter is pressed, the double shutter aperture opens to a predetermined aperture, and then it is closed immediately after maintaining the aperture for a predetermined shutter opening time; In this way, the aperture also acts as a shutter.