Canon A-1 Instructions Manual page 31

through the lens. Each time you move from
one f/stop to the next smaller f/stop (larger
number), the amount of light allowed
through is exactly halved. In effect, the
amount of exposure itself is also halved.
Using f/2 as a st andard, the amount of light
reaching the film will change according to
f/stop as indica ted below.
On the A-1 . , aperture can be controlled
either by turning the AT dial or the lens
aperture ring to the d esired f'/stop. Other-
wise the camera controls the aperture.
£/stop
1.2
1.4
1. S
Brightness ratio 2
j ){
The larges t f/stop on the lens is called the
lens maximum aperture. The smallest f/stop
on the lens is called the lens minimum
aperture. The maximum and minimum
apertures differ accord ing to the lens.
The maximum lens apertur e is important
because it indicates the largest amoun t of
light. that t he lens
wj(J
transmit.
2.8
} . S
4
5.6 8
11 16
22
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