The next element that can control the exposure of an image is SHUTTER SPEED. This is an easy one – it means how fast or slow the shutter in the camera opens and closes again and is a measure of time – seconds, fractions of seconds or sometimes minutes when taking some pictures at night and for astrophotography (forget that for now!).
Light enters the camera lens, comes down the tube of the lens, through the aperture (big or small hole depending on the aperture setting) and then the shutter has to open / close again to expose the camera sensor to the light to form the image. Think of the shutter as a curtain or a set of blinds over the sensor that has to be opened for a specified period of time to get the image (light) to the sensor to record it on your memory card.
Some images don’t need a long time – fractions of a second – to capture enough light to record the image, for example a stationary object during the day; a small amount of light is needed with a quick shutter speed. Others might need several seconds or longer – images taken at night, especially those that capture movement (day or night); lots of light is needed with a longer shutter speed.
Controlling how fast or slow that shutter opens / closes is the shutter speed. On the display of your camera you would see seconds noted as 1″ (1 second), 5″ (5 seconds), etc. Fractions of a second are shown as fractions – 1/2 is half a second, 1/125 is a hundred and twenty fifth of a second, etc. You get the idea.
Easy.
Let’s link this to the aperture though … think of that aperture hole in the lens – if the aperture is wide (small f-stop) it will let in loads of light anyway so you can have a faster shutter speed. But, there is a correlation between the two settings. You can adjust the aperture and the shutter speed in conjunction to achieve the same exposure with different settings…open the aperture and speed up the shutter speed to get the same exposure.
Now, let’s add a third setting into the mix…