A camera is a device used to capture images, as still photographs or as sequences of moving images. The term as well as the modern-day camera evolved from the camera obscura, Latin for "dark chamber", an early mechanism for projecting images, in which an entire room functioned as a real-time imaging system. The camera obscura was first invented by the Iraqi scientist Alhazen and described in his Book of Optics (1011-1021).[1English scientists Robert Boyle and Robert Hooke later invented a portable camera obscura in 1665-1666.
Cameras may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum. A camera generally consists of some kind of enclosed hollow, with an opening or aperture at one end for light to enter, and a recording or viewing surface for capturing the light at the other end. Most cameras have a lens positioned in front of the camera's opening to gather the incoming light and to focus the image, or part of the image, on the recording surface. The diameter of the aperture is often controlled by a diaphragm mechanism, but some cameras have a fixed-size aperture.
Traditional cameras capture light onto photographic film or photographic plate. Video and digital cameras use electronics, usually a charge coupled device (CCD) or sometimes a CMOS sensor to capture images which can be transferred or stored in tape or computer memory inside the camera for later playback or processing.
Cameras that capture many images in sequence are known as movie cameras or as ciné cameras in Europe; those designed for single images are still cameras. However these categories overlap, as still cameras are often used to capture moving images in special effects work and modern digital cameras are often able to trivially switch between still and motion recording modes. A video camera is a category of movie camera which captures images electronically (either using analogue or digital technology).
Stereo camera can take photographs that appear "three-dimensional" by taking two different photographs which are combined to create the illusion of depth in the composite image. Stereo cameras for making 3D prints or slides have two lenses side by side. Stereo cameras for making lenticular prints have 3, 4, 5, or even more lenses. Some film cameras feature date imprinting devices that can print a date on the negative itself.
