Aperture range

The English name of the aperture is Aperture. Aperture is a device that controls the amount of light that passes through the lens and enters the photosensitive surface of the camera. It is usually in the lens. The aperture values ​​F2.8, F8, and F16 we usually refer to are the “coefficients” of the aperture, which are the relative aperture, not the physical aperture of the aperture, and the physical aperture of the aperture and the distance from the lens to the photosensitive device (film or CCD or CMOS). related.

To express the aperture size we use the F value. Aperture F value=focal length of lens/diameter of lens aperture It can be known from the above formula that to achieve the same aperture F value, the aperture of the long focal length lens is larger than that of the short focal length lens.

When the physical aperture of the aperture is not changed, the distance between the center of the lens and the light-sensing device is farther away and the F-number is smaller. Conversely, the closer the distance between the center of the lens and the light-sensing device is, the higher the optical density of light reaching the light-receiving device is, the larger the F-number is. . The complete range of aperture values ​​are as follows: F1, F1.4, F2, F2.8, F4, F5.6, F8, F11, F16, F22, F32, F44, F64.

It is worth mentioning here that the smaller the aperture F value, the greater the amount of light entering the same unit of time, and the amount of light entering the previous stage is just twice that of the next stage. For example, the aperture is adjusted from F8 to F5.6. The amount of light is doubled, and we also say that the aperture has opened a big one. Most non-professional digital camera lenses have a short focal length and a very small physical aperture. The physical aperture of the aperture at F8 is already very small, and the optical phenomena such as diffraction will continue to occur when the camera is zoomed out, affecting imaging. Therefore, the minimum aperture of general non-professional digital cameras is from F8 to F11, while the professional digital camera has a large area of ​​the photosensitive device, the distance between the lens and the photosensitive device, and the aperture value can be very small. For consumer digital cameras, the aperture F value is often between F2.8-F16. In addition, many digital cameras can make 1/3-level adjustments when adjusting the aperture.