9. Exposure is controlled by varying the shutter speed, aperture setting or both. This lever controls the aperture (or diaphragm) and is one of two levers. Lever (9) controls a strip of metal with two holes pressed in it, called Waterhouse stops. Two apertures are available from this lever, wide open (f/4.5) and f/6.3. It is important to note that for f/6.3 to be available the other waterhouse stop MUST be in the f/4.5 position - otherwise the smaller stop of the other lever (10) will be used and the picture will be underexposed.

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