Master the art of modern photography
The camera’s shutter hogged the limelight last issue, and now it’s the turn of its close partner, the lens aperture. While the shutter determines how long the sensor or film is exposed to light, the aperture actually controls how much light reaches the sensor.
Essentially, the aperture is a hole or opening in the lens through which light passes on its way to the sensor. The actual amount of light transmitted is controlled by a device called a diaphragm, which is made up of a number of very thin blades that operate at the very instant of exposure. This is the case with most lenses but there are few exceptions, including fixed aperture and pre-set or manual aperture lenses.
Depending on which aperture value you or the camera has decided to use, the diaphragm will close to a smaller hole, so less light reaches the sensor, or a larger one so that more light passes through. If the lens is set to its widest aperture the diaphragm doesn’t move and the lens will let through as much light as it can.
For a correctly exposed photograph – one with good shadow and highlight detail – the amount of light passing through the lens has to be balanced with how long the light is allowed to hit the sensor. This is the shutter’s job and a speed is selected, again by you or the camera, to give a good result.
As they are the two physical controls fundamental to exposure, the aperture and the shutter work very closely together. To take your photography to the next level, appreciating their reciprocal relationship and how they combine to achieve particular effects is a key skill. We haven’t forgotten the third member of the exposure triangle, though – we’ll be covering ISO in issue 276.
