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8. Controlling the Light The camera provides two primary mechanisms for controlling the amount of light that passes through to the film or sensor: the Aperture and the Shutter Speed. The Aperture controls how much light passes through to the film or sensor by expanding or constricting the opening through which the light passes. Similar to our own eyes dilating, your camera may mechanically grow or shrink the aperture to increase or restrict the amount of light passing through to the film or sensor. You’ll often hear aperture measured in “f-stops”. Unlike you may initially expect, the larger the aperture (the larger the opening for light to pass) the smaller the f-stop designation. So a very large aperture would be reflected by a smaller number, such as f2.0. A very small aperture (a small opening through which light may pass) would be indicated by a large number, such as f16. This is not enough however. As light may constantly pass through the aperture, the camera requires a mechanism by which it can stop light from hitting the film or sensor completely. This mechanism is called the Shutter. It lifts, when you press the shutter release button, to allow light to fall on the film or digital sensor. It then shuts back down in front of the film or digital sensor, blocking the light, in some predetermined amount of time. The Shutter Speed refers to the amount of time the shutter stays open, and subsequently, the amount of time that light is allowed to flow through the aperture and onto the film or sensor. Finally, an obvious, although sometimes overlooked setting that determines the necessary light for proper exposure is the “sensitivity” of the film or digital sensor. We’re probably all familiar with this concept as reflected in the ISO film speeds of traditional cameras. If we were shooting on a bright, sunny day, were encouraged to shoot with IS0 100 or even lower, as there was plenty of light to adequately expose our scenes on relatively less sensitive film. If it was cloudy or dark out, less light necessitated more sensitivity, so we used a higher ISO speed of film, 200, or maybe 400. To ease the transition for photographers from film to digital photography, this idiom was preserved in digital cameras. So you may set the ISO rating for your sensor, although in truth, your actually adjusting the electronic sensitivity of the sensor itself, it has the same net effect, you need less light to properly expose your scenes the higher your ISO rating is set. \ <<PREV 1 2 3 4 5 6 7 8 9 10 11 12 13 NEXT>>
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