Shutter speed

In photography, shutter speed or exposure time is the length of time when the film or digital sensor inside the camera is exposed to light, also when a camera's shutter is open when taking a photograph.The amount of light that reaches the film or image sensor is proportional to the exposure time. ​1⁄500 of a second will let half as much light in as ​1⁄250.Star trails like these are created by using a long exposure to capture the apparent motion of the stars.The Whirligig ride during night at SFGAm at an exposure time of 0.8 seconds.Light streaks outside London Waterloo station.Effect of different shutter speeds on photograph.A 30-second exposure of the rotating New Technology Telescope In photography, shutter speed or exposure time is the length of time when the film or digital sensor inside the camera is exposed to light, also when a camera's shutter is open when taking a photograph.The amount of light that reaches the film or image sensor is proportional to the exposure time. ​1⁄500 of a second will let half as much light in as ​1⁄250. The camera's shutter speed, the lens's aperture or f-stop, and the scene's luminance together determine the amount of light that reaches the film or sensor (the exposure). Exposure value (EV) is a quantity that accounts for the shutter speed and the f-number. Once the sensitivity to light of the recording surface (either film or sensor) is set in numbers expressed in 'ISOs' (ex: 200 ISO, 400 ISO), the light emitted by the scene photographed can be controlled through aperture and shutter-speed to match the film or sensor sensitivity to light. This will achieve a good exposure when all the details of the scene are legible on the photograph. Too much light let into the camera results in an overly pale image (or 'over-exposure') while too little light will result in an overly dark image (or 'under-exposure'). Multiple combinations of shutter speed and f-number can give the same exposure value (E.V.). According to exposure value formula, doubling the exposure time doubles the amount of light (subtracts 1 EV). Reducing the aperture size at multiples of one over the square root of two lets half as much light into the camera, usually at a predefined scale of f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and so on. For example, f/8 lets 4 times more light into the camera as f/16 does. A shutter speed of ​1⁄50 s with an f/4 aperture gives the same exposure value as a ​1⁄100 s shutter speed with an f/2.8 aperture, and also the same exposure value as a ​1⁄200 s shutter speed with an f/2 aperture, or ​1⁄25 s at f/5.6. In addition to its effect on exposure, the shutter speed changes the way movement appears in photographs. Very short shutter speeds can be used to freeze fast-moving subjects, for example at sporting events. Very long shutter speeds are used to intentionally blur a moving subject for effect. Short exposure times are sometimes called 'fast', and long exposure times 'slow'.