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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 standard, the amount of light reaching the film will change according to f/stop as indicated below.

On the A-1, aperture can be controlled either by turning the AT dial or the lens aperture ring to the desired f/stop. Otherwise the camera controls the aperture.

The largest 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 according to the lens. The maximum lens aperture is important because it indicates the largest amount of light that the lens will transmit.

f/stop

1.2

1.4

1.8

2

2.8

3.5

4

5.6

8

11

16

22

Brightness ratio

3

2

1¼

1

½

P

¼

Q

1/16

1/32

1/64

1/128

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