Why can cameras take pictures of scenery?

A camera, referred to as a camera, is a device that uses optical imaging principles to form images and uses film to record the images. Many devices that can record images have the characteristics of a camera. Medical imaging equipment, astronomical observation equipment, etc. 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.

Working Principle

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

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. The camera uses 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, and finally 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 light. When photographing, you must control the appropriate exposure, that is, control the appropriate amount of photons reaching the photosensitive material. Because the amount of photons received by the silver salt photosensitive material has a limited range, too few photons will not form a latent image core, and too many photons will cause overexposure 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. Collection of SLR cameras (23 photos)

From the perspective 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 a camera 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 Curtain 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 path 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.

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 light.