Canon A-1 - Manual (Page 76)

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Selecting an Aperture
A discussion of how to select an appropriate
aperture boils down to an explanation of
depth of field. When your subject is in focus,
there is only a limited range in the fore­
ground and background of the subject which
is also in focus. This zone of sharpness is
called depth of field.
Depth of field is governed by three factors:
aperture, lens focal length and shooting
distance. Remember the following relation­
ships;
(1) The smaller the aperture, the deeper the
depth of field (the other two factors
remaining the same).
For example, if the lens focal length
and the shooting distance stay the same,
the depth of field is much deeper at
f/16 than at f/1.4.
The shorter the lens focal length, the
deeper the depth of field (the other tvvo
•^Aperture priority AE
FD 300mm f/2.8 S.S.C. FLUORITE, f/2.8 ASA 125
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