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The camera uses the linear propagation properties of light and the law of refraction and reflection of light, and uses photons as a carrier to transmit the amount of light information of a scene at a certain moment to the photosensitive material through the photographic lens, and finally becomes a visible image.
The camera's optical imaging system is designed according to the principle of geometric optics, and through the lens, the scene image is accurately focused on the image plane by linear propagation, refraction or reflection of light.
When photographing, it is necessary to control the appropriate amount of exposure, that is, to control the amount of photons that reach the photosensitive material. Because the amount of photon received by the silver salt photosensitive material has a limited range, the photon amount is too small to form a latent image nucleus, and the photon amount is too much to form an overexposure, and the image cannot be distinguished. The camera uses the aperture to change the aperture size of the lens to control the amount of photons per unit time to reach the photosensitive material, and to change the opening and closing time of the shutter to make the exposure time.
From the function of completing photography, the camera generally has three structural systems of imaging, exposure and assistance. The imaging system includes an imaging lens, a ranging focusing, a framing system, an additional lens, a filter, an effect mirror, etc.; the exposure system includes a shutter mechanism, an aperture mechanism, a photometric system, a flash system, a self-timer mechanism, etc.; the auxiliary system includes a winding film Mechanism, counting mechanism, rewinding mechanism, etc.
The lens is an optical system for imaging. It consists of a series of optical lenses and a lens barrel. Each lens has two characteristic data of focal length and relative aperture. The viewfinder is used to select the scene and composition, and is viewed through the viewfinder. The scenes that are in the picture frame can be photographed on the film; the rangefinder can measure the distance of the scene, it is often combined with the viewfinder, and the range and lens can be connected by the linkage mechanism. The focus is linked and the focus is adjusted while the distance is being measured.
Optical fluoroscopy or single-lens reflex finder rangefinders must be manually operated and judged by the naked eye. In addition, there are methods such as photoelectric ranging, sonar ranging, and infrared ranging, which can eliminate manual operation and avoid errors caused by visual judgment to achieve automatic ranging.