In an optical system, the entrance pupil is a virtual aperture that defines the area at the entrance of the system that can accept light. Rays that pass through the pupil are able to enter the optical system and pass through it to the exit (neglecting vignetting). Related topic: List of optical topics Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ... In photography vignetting refer to a reduction in image brightness in the image periphery compared to the image center. ...

The entrance pupil is the image of the aperture stop in the optics that come before it. In a camera, the aperture stop is the diaphragm aperture in the camera that the photographer adjusts to change the f-number. Opening the diaphragm wider increases the size of the pupil, allowing more light to reach the film. For images in Wikipedia, see Wikipedia:Images. ... In optics, an aperture is something which restricts the diameter of the light path through one plane in an optical system. ... In optics, an aperture is something which restricts the diameter of the light path through one plane in an optical system. ... This article is a translation from the Dutch article on diafragma Categories: Stub ... The word aperture means an opening, from the Latin aperire, to open. ... A 35mm lens set to f/11, as indicated by the white dot above the f-stop scale on the aperture ring In photography the f-number (focal ratio) expresses the diameter of the diaphragm aperture in terms of the effective focal length of the lens. ...

The entrance pupil of the eye, which is not quite the same as the physical pupil, is typically about 4 mm in diameter. It can range from 2 mm (f/8.3) in a very brightly lit place to 8 mm (f/2.1) in the dark. This article needs to be cleaned up to conform to a higher standard of quality. ... The human eye The pupil is the central transparent area (showing as black). ...

See also

• Aperture stop
• Exit pupil
• f-number