Canon F-1 Instructions Manual page 25

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Preset
Aperture Ring
30 seconds by using the optional Booster T Finder, a
Index
super sensitive meter finder for measuring subjects under
Aperture
dim light.
Scale
The "60" position is the X synchronization speed,
the highest shutter speed which can be used with
electronic flash units such as a Canon Speedlite, and
the fastest shutter speed at which the entire film area is
exposed at once. Although 1/60th of a second does not
seem to be a really fast shutter speed, the effective
exposure time is equivalent to a flash of 1/1000th of a
"A" Mark
second or faster. This speed allows the very brief
(for AE
duration of the electronic flash to expose the entire film.
photography)
Aperture
EE Lock Pin
Incoming light and depth-of-field are adjusted by turning
the aperture ring to the desired f/stop.
A number scale, which has become the international
standard, has been devised to express the size of the
aperture in relation to the focal length of the lens
whereby the aperture size is divided by the focal length
of the lens until the numerator of the resulting fraction
is reduced to one. Thus, the magnitude of these fractions
is inversely related to the size of the aperture, i.e., a
larger number on the scale signifies a smaller aperture
while a smaller number signifies a larger aperture. Since
both circular area and linear dimension are involved in
the computation of this scale, an aperture, usually
termed a full f/stop, is one-half or twice as large as the
adjacent apertures indicated by the scale.
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