A camera that takes pictures immediately after taking them

It should be called a printing plate camera.

A camera is an optical instrument used for photography. After the light reflected from the scene being photographed is focused through the photographic lens (objective lens) and the shutter that controls the exposure, the scene being photographed forms a latent image on the photosensitive material in the camera obscura, which is then processed (i.e. developed, fixed) to form a permanent image. image, this technique is called photography.

The earliest camera structure was very simple, including only a camera obscura, a lens and photosensitive materials. Modern cameras are relatively complex, with systems such as lens, aperture, shutter, ranging, framing, metering, film transport, counting, and Selfie. It is a complex product that combines optics, precision machinery, electronic technology, chemistry and other technologies.

Before 400 BC, there were records of pinhole imaging in the "Mo Jing" written by Mozi; in the 13th century, image obscura made using the principle of pinhole imaging appeared in Europe, and people Walk into the camera obscura to watch images or paint scenes; in 1550, Italy's Cardano placed the lenticular lens in the original pinhole position, and the image effect was brighter and clearer than the camera obscura; in 1558, Italy's Barbaro made another The addition of an aperture to Dano's device greatly improved the image clarity; in 1665, the German monk John Chapter designed and produced a small, portable single-lens reflex camera obscura. Because there was no photosensitive material at the time, this camera obscura only Can be used for painting.

In 1822, Niépce of France produced the world's first photograph on photosensitive material, but the image was not very clear and required eight hours of exposure. In 1826, he took a photo through a camera obscura on a tin base plate coated with photosensitive asphalt.

In 1839, Daguerre of France made the first practical daguerreotype camera. It was composed of two wooden boxes. One wooden box was inserted into the other to adjust the focus. Use the lens cap as a shutter to control exposure times of up to thirty minutes to capture clear images.

In 1860, Sutton of England designed a primitive single-lens reflex camera with a rotatable mirror viewfinder; in 1862, Detry of France stacked two cameras together to create a Only taking pictures and taking pictures constitutes the original form of a double-lens camera; in 1880, Baker in England made a double-lens reflex camera.

With the development of photosensitive materials, dry plates coated with silver bromide photosensitive material appeared in 1871, and in 1884, films using nitrocellulose (celluloid) as the base film appeared.

With the advent of magnification technology and micro-grain film, the quality of lenses improved accordingly. In 1902, Rudolf of Germany used the third-order aberration theory established by Seidel in 1855 and the high refractive index and low dispersion optical glass successfully studied by Abbe in 1881 to create the famous "Tiansai" lens. The reduction of various aberrations greatly improves the imaging quality. On this basis, in 1913, Barnack in Germany designed and produced a small Leica camera using 35mm film with small holes in the negative.

However, 35mm cameras of this period all used see-through viewfinders without a rangefinder. Color film was made in 1930; in 1931, Germany's Contax camera was equipped with a double-image coincidence rangefinder using the triangular ranging principle, which improved the focusing accuracy, and was the first to adopt an aluminum alloy die-cast body and Metal curtain shutter.

In 1935, the Exact single-lens reflex camera appeared in Germany, making it easier to adjust focus and change lenses. In order to ensure accurate camera exposure, Kodak cameras began to be equipped with selenium photocell exposure meters in 1938. In 1947, Germany began to produce the Contax S-shaped roof pentaprism single-lens reflex camera, which made the viewfinder image no longer upside down, and changed the downward view to the head-up focusing and framing, making photography more convenient.

In 1956, the Federal Republic of Germany first made an electric eye camera that automatically controlled exposure; after 1960, cameras began to adopt electronic technology, and various forms of automatic exposure and electronic program shutters appeared; after 1975, Camera operations began to become automated.

There are many kinds of cameras, which can be divided into landscape photography cameras, printing and platemaking cameras, document microfilm cameras, microscope cameras, underwater cameras, aerial cameras, high-speed cameras, etc. according to their uses; according to the size of the film, they can be divided into For 110 camera (frame 13×17 mm), 126 camera (frame 28×28 mm), 135 camera (frame 24×18, 24×36 mm), 127 camera (frame 45x45 mm), 120 camera (including 220 camera, Screen 60×45, 60×60, 60×90 mm), disc camera (screen 8.2x10.6 mm); according to the viewing method, it is divided into perspective view camera, twin-lens reflex camera and single-lens reflex camera.

No classification method can include all cameras, and a certain camera can be divided into several categories. For example, 135 cameras are classified according to their framing, shutter, metering, film transfer, exposure, flash, and adjustment. The differences in focusing, selfie and other methods form a complex spectrum.

Cameras use the linear propagation properties of light and the laws of refraction and reflection of light, using photons as carriers, to transfer the amount of light information of the scene being photographed at a certain moment to the photosensitive material through the camera lens in the form of energy. Finally, it becomes a visible image.

The optical imaging system of the camera is designed according to the principles of geometric optics, and through the lens, the scene image is accurately focused on the image plane through the straight-line propagation, refraction or reflection of the light.

When taking photography, it is necessary to control the appropriate exposure, that is, to control the appropriate amount of photons reaching the photosensitive material. Because there is a limited range in the amount of photons that the silver salt photosensitive material can receive. If the amount of photons is too small, latent image nuclei will not be formed. If the amount of photons is too much, overexposure will occur, and the image cannot be distinguished. The camera uses the aperture to change the light aperture of the lens to control the amount of photons reaching the photosensitive material per unit time, and at the same time changes the opening and closing time of the shutter to control the length of the exposure time.

In terms of completing the function of photography, a camera generally has three major structural systems: imaging, exposure and auxiliary systems. The imaging system includes imaging lenses, range-finding focusing, viewfinder systems, additional lenses, filters, effect lenses, etc.; the exposure system includes shutter mechanisms, aperture mechanisms, metering systems, flash systems, self-timer mechanisms, etc.; auxiliary systems include film winding Mechanism, counting mechanism, film rewinding mechanism, etc.

The lens is an optical system used for imaging, consisting of a series of optical lenses and lens barrels. Each lens has two characteristic data: focal length and relative aperture; the viewfinder is used to select scenes and compose images. A device that allows any part of the scene seen through the viewfinder to fall within the frame of the picture to be photographed on film; a rangefinder can measure the distance of the scene, and is often combined with the viewfinder to The mechanism can link distance measurement and lens focusing, and complete focus adjustment while measuring distance.

Optical see-through or single-lens reflex viewfinder rangefinders must be operated manually and judged by the naked eye. In addition, there are photoelectric ranging, sonar ranging, infrared ranging and other methods, which can eliminate manual operation and avoid errors caused by naked eye judgment to achieve automatic ranging.

The shutter is the main component for controlling exposure. The most common shutters are lens shutter and focal plane shutter. The lens shutter is composed of a set of very thin metal blades. Under the action of the main spring, the action of the connecting rod and the dial causes the blades to open and close quickly; the focal plane shutter is composed of two sets of partially overlapping curtains (front curtains). and rear curtain), installed near the front of the focal plane. The two curtains are activated in sequence to form a gap. The slit is swept across the front of the film to achieve the exposure.

Aperture, also called diaphragm, is a mechanism that limits the passage of light beams and is installed in the middle or behind the lens. Aperture changes the diameter of the light and controls exposure together with the shutter. Common apertures include continuously variable and discontinuous apertures.

The Selfie mechanism is a device that acts as a delay during the photography process to allow photographers to take selfies. When using the Selfie mechanism, first release the delayer, and then automatically release the shutter after the delay. There are two types of Selfie mechanisms: mechanical and electronic. The mechanical Selfie mechanism is a gear-driven delay mechanism that can generally delay for 8 to 12 seconds. The electronic Selfie mechanism uses an electronic delay circuit to control the shutter release.