What's so particular about photography aperture?

General formula: F value of aperture = lens focal length/effective aperture.

1, aperture /F

The abbreviation of aperture is f, and the value of F2.8 displayed on the DC screen is aperture 2.8. The aperture value is inversely proportional to the aperture size, and the smaller the aperture value, the larger the aperture.

Common aperture values are as follows: F 1, F 1.4, F2, F2.8, F4, F5.6, F8, f1,F 16, F22, F32, F44.

For example, if the aperture is adjusted from F4 to F2.8, the amount of light entering will double; From F2.8 to F2, it has doubled. The aperture value is opposite to the actual size of the aperture. The aperture is F 1 when the light input is maximum, and F64 when the light input is minimum. For 135 camera, the minimum aperture of most lenses is F22.

2. Shutter

Shutter is a device used by camera to control exposure time. The inside of the camera is like a cassette, the shutter is the lid of the box, and the size of the lid is the aperture. The longer the cover is opened, the more light will come in and the brighter the photo will be.

Shutters include mechanical shutter, electronic shutter and electromechanical combination shutter. The unit of the shutter value is seconds. For example, the value displayed on the DC screen is 1/30, which means that the shutter speed is 1/30 seconds (meaning from opening the lid of the box to closing 1/30 seconds). The way to mark the shutter is usually to display only the denominator value.

Safety shutter means that the camera won't blur the photo when the human body shakes slightly for a limited number of seconds. The hand shock prevention function on DC will slightly improve the safety shutter, but it is not omnipotent. The safety shutter of a hand-held camera is the reciprocal of the focal length, that is, if the focal length is 35mm, the safety shutter is 1/35s, and if the focal length is 200mm, the safety shutter is 1/200s.

When using DC, I always set the lowest (slow) shutter speed to 1/30 seconds. If the shutter speed exceeds 1/30 seconds, I need to adjust the ISO value and aperture size. If you have used the maximum aperture and the highest ISO value, you can only use a tripod or put it on a safe plane to shoot, otherwise the picture may be burnt.

3, ISO/ sensitivity

ISO sensitivity is the sensitivity of CCD/CMOS (or film) to light. If ISO 100 film is used, if the camera can correctly expose within 2 seconds, then under the same light conditions, it only takes 1 second to use ISO200 film and 0.5 second to use ISO400 film.

In the digital age, there are ISO options in the main menu of digital cameras, such as 100, 200, 400 or 800, just like those on film. Depending on the model, from ISO50 to 25600, the higher the number, the more sensitive it is.

Extended data:

The function of aperture:

1, which can adjust the amount of light entering the lens. For example, domestic kittens always shrink their pupils into a line during the day, and automatically Zhang Kaicheng a round hole at night. So in the same way, when taking pictures, the aperture should be narrowed when the light is strong, and the aperture should be opened when the light is dark. That is to say, the smaller the F value (other parameters remain unchanged), the more favorable it is for shooting at night.

The adjusting ring on the rotating lens or the knob on the digital camera body is used to adjust the aperture size.

2. Aperture is the most important factor to determine the depth of field. Small aperture (large aperture value), depth of field, large aperture (small aperture value), depth of field! For example, nearsighted friends, if they don't wear glasses, always habitually squint at things, so they can often see things clearly. To use photographic terminology, this is called: narrowing the aperture (pupil) and increasing the depth of field!

References:

Baidu encyclopedia-aperture

Baidu encyclopedia-shutter