Aperture is one of the three pillars of photography, the others being shutter speed and ISO. It is simply a hole which allows light into the camera. Aperture is measured by the f/stop.
In photography, aperture controls two aspects which are depth of field and exposure.
Depth of field affects how blurry the background is:
If a lower f/stop is used (e.g. f2.8), the depth of field is shallower, resulting in a blurrier background. A shallow depth of field is perfect for portraits where you want a subject to stand out. By blurring out the background, distracting details in the background are minimised.
If a higher f/stop is used (e.g. f8), the depth of field is deeper, resulting in a sharper background. This is ideal for landscape photos where you want sharp details in both the foreground and background. Also ideal for large group photos where there are two or more rows of people and you want everyone’s face to be clearly visible.
Below is an an image with a lower f/stop of 2.8. Notice how the detail of the plant is blurry. To the right is an image with a higher f/stop of 13. Notice how the detail of the plant is sharper.
Exposure determines how bright or dark a photograph is;
If a lower f/stop is used (such as f/2.8), the image will be brighter. This happens because the aperture is wider, resulting in more light entering the camera.
If a higher f/stop is used (such as f/13), the image will be darker. This happens because the aperture is smaller, resulting in less light entering the camera.
Below, you can see how the exposure changes when only the aperture is changed.
Have a go! Whip out your DSLR and put it on full manual mode (including ISO). Experiment by changing only the aperture and seeing how it impacts the depth of field and exposure.
If you want to solely change the depth of field, try shooting in Aperture value mode (likely marked on your DSLR’s dial by ‘Av’ on Canon and Pentax cameras, while by ‘A’ on Nikon and Olympus cameras). In this mode, the camera will automatically set the exposure level by compensating in accordance to which f/stop you use.
I hope this tip on Aperture will help you get more creative with your photography.