Long exposure, wide depth of field: f/11 for 1/8 second, ISO200
The word photography comes from the ancient Greek: photos (light). Understanding and mastering exposure is therefore essential in the art of photography. The shutter speed, the (diaphragm) aperture and the ISO are the three elements, which form the triangle of exposure.
The shutter speed is determined by how long the shutter stays open. The sensor in digital cameras will capture more light when the shutter stays open longer. A slow shutter speed (for example 1/10 second) can be used in low-light environment or to create a motion blur (waterfalls, rain streaks) while a fast shutter speed (for example 1/1000 second) is used to freeze a movement like a bird in flight.
Fast exposure, short depth of field: f/5.6 for 1/800 second, ISO1250
The aperture (f/N) is short for diaphragm aperture. A small aperture like f/22 does not allow a lot of light to pass through the lens, however it provides a wide depth of field and is commonly used in landscape photography. A big aperture like f/5.6 lets more light pass through the lens and it also provides a narrow or short depth of field.
The ISO is related to the film sensitivity to light or image sensor’s sensitivity to light on digital cameras. On a sunny day, photographers typically use a low ISO (100) but in low-light situation (overcast day, night), they increase the ISO. Note that a high ISO (3,200 or more) will create noise in your image (grainy veil).