The most basic type of camera was invented during the 16th century. This 'first camera' was referred to as a 'camera obscura'. This device used a dark room as a projection chamber. A small hole in one wall acted as a lens, which projected an image of whatever was outside upside down on the opposing wall. A camera obscura is not really a camera in the modern sense; it only projected an image. The ability to record an image was not invented until the 19th century. The camera obscura was used both for entertainment and a tool for tracing. The camera obscura lead to future developments in camera technology. It also is an excellent illustration of the basic parts of the two basic parts a camera must have. All cameras have an aperture, or an opening that admits light and either a developable surface or a viewing surface. In most cases there is a dark chamber between the aperture and the developable surface. Most cameras have a lens that allows the image to be focused.
The simplest cameras are fixed-focus lenses - they are designed so that objects within a certain distance are more or less focused. The next most complex focusing method employs three or four fixed focus adjustments that the photographer can choose from based on the distance of the object being photographed. Even more complex are lenses that the photographer can adjust to focus on an object at a specific distance. User-adjustable lenses are often used on cameras fitted with a device that allows the photographer to determine if the subject is in focus. Some cameras are fitted with a rangefinder which allows focus to be set solely based on distance. Single lens reflex cameras use a mirror that diverts the image to a viewing eyepiece. This allows the photographer to see the image as it will be recorded on film. Focus can be adjusted until the desired subject is clear. This design is superior to a twin reflex camera, where there are two identical lenses. One lens records the image and the second lens displays the image on a viewing screen. At most distances the two images are identical, but at close range some parts of the recorded image may be cropped.
Cine cameras, or movie cameras, have similar lens configurations as still cameras. The difference is that they take a rapid series of images. When the images are re-played at the same speed they were taken it creates the illusion that the image is moving.