Control
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Description
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Focus
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The position of a viewed object or the adjustment of an optical
device necessary to produce a clear image: in focus; out of focus.
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Aperture
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Adjustment of the lens opening, measured as f-number, which controls
the amount of light passing through the lens. Aperture also has an effect on
depth of field and diffraction – the higher the f-number, the smaller the
opening, the less light, greater the depth of field, and the more the
diffraction blur. The focal length divided by the f-number gives the
effective aperture diameter.
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Shutter speed
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Adjustment of the speed (often expressed either as fractions of
seconds or as an angle, with mechanical shutters) of the shutter to control
the amount of time during which the imaging medium is exposed to light for
each exposure. Shutter speed may be used to control the amount of light
striking the image plane; 'faster' shutter speeds (that is, those of shorter
duration) decrease both the amount of light and the amount of image blurring
from motion of the subject and/or camera.
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White balance
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On digital cameras, electronic compensation for the color temperature
associated with a given set of lighting conditions, ensuring that white light
is registered as such on the imaging chip and therefore that the colors in
the frame will appear natural. On mechanical, film-based cameras, this
function is served by the operator's choice of film stock or with color
correction filters. In addition to using white balance to register natural
coloration of the image, photographers may employ white balance to aesthetic
end, for example white balancing to a blue object in order to obtain a warm
color temperature.
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Metering
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Measurement of exposure so that highlights and shadows are exposed
according to the photographer's wishes. Many modern cameras meter and set
exposure automatically. Before automatic exposure, correct exposure was
accomplished with the use of a separate light metering device or by the
photographer's knowledge and experience of gauging correct settings. To
translate the amount of light into a usable aperture and shutter speed, the meter
needs to adjust for the sensitivity of the film or sensor to light. This is
done by setting the "film speed" or ISO sensitivity into the meter.
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ISO speed
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Traditionally used to "tell the camera" the film speed of
the selected film on film cameras, ISO speeds are employed on modern digital
cameras as an indication of the system's gain from light to numerical output
and to control the automatic exposure system. The higher the ISO number the
greater the film sensitivity to light, whereas with a lower ISO number, the film
is less sensitive to light. A correct combination of ISO speed, aperture, and
shutter speed leads to an image that is neither too dark nor too light, hence
it is 'correctly exposed', indicated by a centered meter.
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Auto focus point
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On some cameras, the selection of a point in the imaging frame upon
which the auto-focus system will attempt to focus. Many Single-lens reflex
cameras (SLR) feature multiple auto-focus points in the viewfinder.
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References: www.wikipedia.org
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