Do you know the basic knowledge of SLR-long exposure noise reduction?

The lens is like a human eye. Maybe you go around a big circle, and finally you find that photography is just a blink of an eye, just a simple combination of aperture and shutter.

1. hole

Aperture is a device used to control the amount of light entering the photosensitive surface of the fuselage through the lens. Generally speaking, in a lens, the aperture size is expressed by F value. For the manufactured lens, the diameter of the lens cannot be changed at will, but the luminous flux of the lens can be controlled by adding a polygon or circular hole grating with variable area inside the lens. This device is called an aperture.

In order to accurately control the exposure, there are a series of apertures. Common aperture values are 1, 1.4, 2, 2.8, 4, 5.6, 8, 1 1, 16, 22, 32, where each number represents the first-order aperture, and the luminous flux between each aperture is different. The smaller the number, the greater the luminous flux.

2. 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 longer the shutter time range, the better.

In order to accurately control the exposure, the shutters are also arranged in grades. For example, 4 seconds, 2 seconds, 1 second, 1/2 seconds, 1/4 seconds, 1/8 seconds,1/0/5 seconds, 1/30 seconds.

3. Combination of aperture and shutter

The aperture and shutter have their own values, so there is a corresponding relationship. For example, when shooting, the aperture is 5.6 and the shutter takes 1/250 seconds. If you want to get the same exposure, you can increase the aperture by one step, use 4, reduce the speed shutter by one step, and use 1/500. Or the aperture is small 8, and the shutter is slow1125 seconds.

We can use a variety of different aperture shutter combinations to get the same exposure, but the photo effect obtained by each combination is different. For example, the following picture shows the same exposure, but the clear range of the subject before and after is different.

This involves the depth of field, that is, the clear range before and after the focus subject. Large depth of field and wide definition range; Small depth of field and clear range. When applied to aperture, the larger the aperture (the smaller the aperture value), the smaller the depth of field; The smaller the aperture, the greater the depth of field.

If it is applied to actual shooting, it is necessary to highlight the subject, blur the background and use a large aperture when shooting people; When shooting scenery, the scenery from near to far is very clear, so use a small aperture.

Through different combinations of aperture and shutter, different visual effects of photos can be achieved.