What is a Brief Introduction to Photography (2)

Shutter The shutter of a camera is a mechanical device that controls the exposure time. The shutter is always closed to prevent exposure of the negative film in the camera. Turn it on and off when shooting, so that the image light passing through the lens acts on the film.

The first function of the shutter is to control the amount of light passing through people by the length of the opening time. When the brightness of the subject and the aperture of the lens remain unchanged, the longer the shutter is opened, the more light will act on the film. The shorter the shutter opening time, the less light will act on the film. The length of shutter opening time is called shutter speed. Second, with the aperture exposure, the correct photographic exposure can take photos with rich levels and clear details. Therefore, the shutter speed and aperture must be properly matched according to the film speed and aperture intensity.

Exposure value and exposure value used a certain speed of film combined with shutter speed and aperture coefficient to represent exposure value.

For some purposes, it is necessary to use a lens to block certain wavelengths of light from entering the camera through the lens, or to restrict its passage. This lens is called a filter, also called a color filter.

Contrast filter is used to change a certain tone of the subject in black and white photography to improve the contrast, also known as contrast filter. The application principle of contrast filter is to use a filter that penetrates a certain color in the photo when it is bright and a filter that absorbs a certain color when it is dark.

Ultraviolet filter is called UV for short. Ultraviolet light is invisible light, but film is very sensitive to it. Therefore, when shooting scenes, ultraviolet filters should be used to absorb distant ultraviolet rays, so as to reduce its influence on the negative film and enhance the clarity of the image. Also known as the mirror of the sky, it is also the nature of ultraviolet filter.

Neutral color filter is called ND for short. Neutral color filters have the same absorption rate for all kinds of light, which is used to reduce the amount of light passing through the lens. When the minimum aperture or the fastest shutter is used and overexposed, a neutral filter is needed to reduce the exposure value. There are three types: double, four and eight. The so-called multiple refers to exposure multiple.

Polarization filter, PL for short, is composed of many tiny crystals with the same direction. The light reflected from a certain angle from the sky, water surface and non-metallic smooth surface will be polarized. If a polarizer is installed on the lens, these reflections can be controlled, eliminated or weakened to show the texture of the object. It has the following four functions:

1. Control the hue of the sky: If you want to deepen the hue of the blue sky in color photography, you can use a polarizer, and the hue of trees and water will be enhanced by partial reflection.

2. Control the reflection of objects: It is reasonable to control the light reflected by non-metallic smooth surfaces with polarizers, such as shooting the goods in the window or the underwater scenery across the water surface, in which it is more effective to tilt the reflecting surface by about 30 degrees.

3. Improve the chroma.

4. Replace the neutral color filter: the exposure multiple of the polarizing filter is similar to four times ND, so the former can replace the latter.

The infrared filter absorbs all visible light except ultraviolet rays and only lets infrared rays pass through. Committed to infrared film photography.

The color film of the color temperature balance filter is designed for the standard color temperature, which balances the color sense and speed of the blue-green-red three-layer emulsion and achieves color balance. However, the color temperature of sunlight is different from morning to dusk, so is the color temperature of cloudy and sunny days, and the color temperature of light is different due to voltage. When the color temperature of light source does not meet the requirements of film color temperature, color cast will appear, and color temperature balance filter is needed.