A wide variety of cameras, by use can be divided into landscape photography cameras, printing plate camera,
Documentation miniature cameras, microscopic cameras, underwater cameras, aerial cameras, high speed cameras, etc., according to phase film size, can be divided into 110 cameras (screen 13x17 mm), 126 cameras (screen 28x28 mm), 135 cameras (screen 24x18,24x36 mm), 127 cameras (screen 45x45 mm), 120 cameras (including 220 cameras, screen 60x45,60x60,60x90 mm), disc cameras (picture 8.2x10.6 mm); the way of framing is divided into perspective camera, double lens reflective camera, single lens reflective camera.
Any classification method can not include all cameras, a camera can be divided into several categories, such as 135 cameras according to its frame, shutter, metering, transmission, exposure, flash, focusing, self-portraits and other ways of different, constitutes a complex spectrum. The camera uses the linear propagation of light and the refraction and reflection of light, the photon as the carrier, a moment of the light information of the scene, the energy of the photographic lens transmitted to the photosensitive material, eventually become visual image. The optical imaging system of the camera is designed according to the principle of geometric optics, and through the lens, the image is accurately focused on the image plane by spreading, refraction, or reflection through the line of light. In photography, the appropriate exposure must be controlled, i.e. the appropriate amount of photons to reach the photosensitive material. Because silver-salt photosensitive materials receive the amount of photon has a limited scope, the photon amount is too little latent shadow nucleus, the photon quantity has formed excessive exposure, the image can not distinguish. Cameras are optical circles to change the lens light aperture size, to control the unit time to reach the photosensitive material of the photon amount, while changing the shutter opening and closing time to control the length of exposure time.