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Basic Terminology
Depth of field
This is the range where acceptable focus can be achieved in front of and behind the point of
the subject. The smaller the aperture (the higher the f/number), the deeper the depth of field.
And the larger the aperture (the lower the f/number), the shallower the depth of field.
The depth of field is affected as described below:
(1) A smaller aperture (a higher f/number) increases the depth of field.
For example, stopping down to f/8 obtains a deeper depth of field than f/4.5.
(2) A lens with a shorter focal length increases the depth of field.
A wide-angle lens obtains a deeper depth of field than a telephoto lens.
(3) A longer distance between the camera and subject increases the depth of field.
(4) The depth of field behind the point of optimum focus (2) is longer than the depth of field in
front of the point of optimum focus (1).
1
2
Depth of field
Point of optimum focus
Aperture set to f/22.
Aperture set to f/2.
Exposure
Exposure occurs when the film (or the image sensor in a digital camera) is exposed to light.
Correct exposure is obtained when the film or the image sensor is exposed to a proper amount
of light in accordance with its sensitivity to light. The correct exposure is adjusted with the
camera's shutter speed and aperture.
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