For beginners and amateurs, the hardest part of photography can be the daunting amount of confusing technical terms. Listed below are a few common terms with easy to understand explanations.
Aperture
This refers to a diaphragm inside all cameras which change size to admit more or less light. This structure is very similar to how the human eye works in that a circular opening becomes enlarged or smaller dependent upon how much light there is.
The most confusing thing about aperture is the nomenclature used. It is quoted in what are called f-stops. A smaller f-stop number, for example f/1.8, actually means that the aperture will open wider, while a larger f-stop, for example f/22, means only a tiny opening.
Unless it is an SLR, your camera will have a range of available f-stops, for example f/2.8-f/8. This means that the widest the aperture can open is f/2.8 and the narrowest, f/8.
Sensor
When you press the button to take a photo, the camera contains a light-sensitive panel that records the light hitting it at the time. This function in a digital camera performs the same function as film does in a film camera. This sensor is hidden behind the shutter (see below) and is not exposed until the button is pressed. Light is recorded by the sensor when a photo is taken and stored on a memory card.
Shutter Speed
A cameras shutter sits just in front of the image sensor. It is normally closed so that no light is getting through to the sensor, but when you press the button, it opens for a certain length of time to expose the sensor to light.
Most shutters are actually composed of two curtains. At a fast shutter speed, the first curtain opens only a tiny gap between it and the second curtain, and travels across the sensor with the second curtain following close behind. For longer exposures the whole sensor might be exposed for a period of time before the second curtain closes it.
Shutter speeds are expressed in whole and fractions of seconds. A shutter speed of 1/640, for example, means that the sensor will be exposed for only a one-six-hundred-and-fortieth of a second.
Exposure
Exposure is so named because it refers to exposing the sensor or film to light in order to take a photograph. An exposure is also another name for a photograph for this reason.
As a photograph is taken, how much light reaches the light-sensitive sensor is determined by aperture and shutter speed. If a darker photo is desired, a slower shutter speed and larger aperture or combination of both may be required for a quality photograph.
A correct exposure is one that approximates what could be seen by the photographer with the naked eye at the time the photo was taken, but this is ultimately a matter of taste. It is possible, for example, to take photos at night with shutter speeds so long that the resulting photos look as if they were taken in broad daylight.
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