What is the reflection of photography?

It is convex lens imaging, and the camera is an optical instrument used for photography. After the light reflected by the shot scene is focused by the camera lens (scene lens) and the shutter for controlling exposure, the shot scene forms a latent image on the photosensitive material in the camera box, and forms a permanent image after being developed and fixed. This technology is called photography.

The earliest camera structure was very simple, including only a black box, a lens and photosensitive materials. Modern cameras are more complicated, including lens, aperture, shutter, ranging, framing, metering, film transmission, counting, self-timer and other systems. It is a complex product integrating optics, precision machinery, electronic technology and chemistry.

Before 400 BC, Mozi recorded pinhole imaging in Mo Jing. /kloc-in the 0/3rd century, an image black box made by pinhole imaging principle appeared in Europe. People walked into the black box to watch images or paint landscapes. 1550, the Italian cardano put the lenticular lens in the original pinhole position, and the imaging effect is brighter and clearer than the black box; 1558, the Italian Barbaro added an aperture to the device in cardano, which greatly improved the imaging clarity. 1665, John Zhang, a German monk, designed and manufactured a small portable single-lens reflective image camera box, because there was no photosensitive material at that time, and this camera box could only be used for painting.

1822, the Frenchman Niepce made the world's first photo on the photosensitive material, but the image was not clear and needed eight hours of exposure. In 1826, he took a photo through a black box on the tin floor coated with photosensitive asphalt.

1839, Frenchman Daguerre made the first practical silver camera, which consisted of two wooden cases. One wooden box is inserted into another to focus, and the lens cover is used as a shutter to control the exposure time for up to 30 minutes, so that a clear image can be taken.

1860, Sutton, England designed the first single-lens reflex camera with a rotatable viewfinder. 1862, Detrie, a Frenchman, stacked two cameras together, one for taking pictures and the other for taking pictures, forming the prototype of a dual-lens camera. 1880, Baker of England made a double-lens reflex camera.

With the development of photosensitive materials, dry plates coated with silver bromide photosensitive materials appeared in 187 1 year, and films based on nitrocellulose (celluloid) appeared in 1884.

With the appearance of magnifying technology and particle film, the quality of lens has been improved accordingly. In 1902, Rudolf made a famous "Tiansai" lens by using the third-order aberration theory established by Cedell in 1855 and the high refractive index and low dispersion optical glass successfully researched by Abbe in188/0/year. Due to the reduction of various aberrations, the imaging quality is greatly improved. On this basis, in 19 13, a small Lycra camera with 35 mm film punched in the negative was designed and manufactured in Barnach, Germany.

However, all the 35 mm cameras in this period used perspective viewfinders without rangefinders. 1930 to make color film; 193 1 Germany Contex camera has been equipped with a double-image coincidence rangefinder based on the principle of triangular ranging, which improves the focusing accuracy, and adopts aluminum alloy die-casting body and metal curtain shutter for the first time.

1935, a single-lens reflex camera of Ek Saquetoux appeared in Germany, making it easier to focus and change lenses. In order to make the camera exposure accurate, Kodak camera began to install selenium photocell exposure meter at 1938. 1947, Germany began to produce Contax S five-prism single-lens reflex camera, which made the viewfinder image no longer upside down, and changed the top view to head-up focusing framing, making photography more convenient.

1956, the Federal Republic of Germany first manufactured an electric eye camera with automatic exposure control; After 1960, cameras began to adopt electronic technology, and many forms of automatic exposure and electronic program shutters appeared; 1975, the operation of the camera began to be automated.

There are many kinds of cameras, which can be divided into landscape cameras, printing and plate-making cameras, document microfilm cameras, microscopic cameras, underwater cameras, aerial cameras, high-speed cameras and so on. According to the size of photographic film, it can be divided into 1 10 camera (picture 13× 17mm), 126 camera (picture 28× 28mm) and 135 camera (picture 24×/kloc).

Any classification method cannot include all cameras, and a camera can be divided into several categories. For example, 135 camera forms a complex spectrum according to its different ways of framing, shutter, metering, film transmission, exposure, flashing, focusing and self-timer.

The camera uses the linear propagation characteristics of light and the law of refraction and reflection of light, takes photons as the carrier, and transmits the light information of the shooting scene to the photosensitive material in the form of energy through the photographic lens, and finally becomes a visible image.

The optical imaging system of the camera is designed according to the principle of geometric optics. Through the lens, the scene image is accurately focused on the image plane through the linear propagation, refraction or reflection of light.

Proper exposure should be controlled when taking pictures, that is, the amount of photons reaching the photosensitive material should be controlled properly. Because the range of photons received by silver salt photosensitive materials is limited, too few photons form latent image nuclei, and too many photons form overexposure, so the image cannot be distinguished. The camera uses the aperture to change the aperture of the lens to control the amount of photons reaching the photosensitive material in a unit time, and at the same time, the exposure time is determined by changing the opening and closing time of the shutter.

As far as the function of photography is concerned, a camera should have three structural systems: imaging, exposure and assistance. The imaging system includes imaging lens, ranging and focusing, framing system, additional lens, filter, effect mirror and so on. Exposure system includes shutter mechanism, aperture mechanism, metering system, flash system, self-timer mechanism, etc. The auxiliary system includes a film winding mechanism, a counting mechanism and a film rewinding mechanism.

Lens is an optical system for imaging, which consists of a series of optical lenses and lens barrels. Each lens has two characteristic data: focal length and relative aperture. The viewfinder is a device for selecting scenery and composition. Everything you can see through the viewfinder can be shot on film. A rangefinder can measure the distance of a scene, and it is often combined with a viewfinder. Through the linkage mechanism, ranging can be linked with lens focusing and focus can be completed at the same time.

Optical perspective or single-lens reflective viewfinder rangefinder must be operated manually and judged by naked eyes. In addition, there are photoelectric ranging, sonar ranging, infrared ranging and other methods, which can avoid manual operation, avoid the error caused by naked eye judgment and realize automatic ranging.

Shutter is the main component to control exposure. The most common shutters are lens shutter and focal plane shutter. The lens shutter consists of a group of thin metal blades. Under the action of the main spring, the blade is quickly opened and closed under the action of the connecting rod and the shifting ring. The focal plane shutter is composed of two sets of partially overlapped curtains (front curtain and Hou Lian), which are installed near the front of the focal plane. Two curtains are activated to form a gap. The gap is swept in front of the film to realize exposure.

Aperture, also called diaphragm, is a mechanism to limit the passage of light beams, which is installed in the middle or behind the lens. Aperture can change the aperture of energy light and control the exposure together with the shutter. There are two kinds of common apertures: continuous variable aperture and discontinuous variable aperture.

Self-timer mechanism is a device that plays a delaying role in the process of photography for photographers to take selfies. When using the self-timer mechanism, first release the delay device, and then automatically release the shutter after the delay. There are two self-timer mechanisms: mechanical and electronic. The mechanical self-timer mechanism is a gear-driven delay mechanism, which can generally delay 8 ~ 12 seconds. Electronic selfie mechanism uses electronic delay line to control shutter release.