Clever son

My son just started studying photography for his A Levels. He's really into it - so enthusiastic about the assignments! He took these photos to show the differences in depth of field with different apertures - I love the color combinations he's used here. And below is what he wrote about aperture, which explains it better than I ever could!
 

What is aperture?

An aperture is a hole that is made out of several blades that allows light to travel into the camera. The size of the aperture is measured in f-stops, for example: when the aperture is fully opened it is at f/2.8 and when the aperture is almost closed it is at f/22. Some lenses can reach an aperture less then f/2.8 and above f/22. The aperture doesn’t only control the amount of light entered in, it also controls how ­much depth of field is put into the photo (as seen below). When the aperture is at a higher f-stop (f/22, smaller hole), it can let the foreground and the background be in compete focus but let less light in. When the aperture is at a lower f-stop (f/2.8, bigger hole), it can only focus on one thing but can also let more light into the camera. The first photo below shows the result of f/2.8 as the background is out of focus whilst the foreground is in focus. As the aperture gets smaller it can focus on more objects but let less light in. From the point where the camera is not focused, to the point where the camera is focused, is known as depth of field.