“Use a combination of wide apertures, long focal lengths and close viewpoints to take a number of photographs with shallow depth of field. (Remember that smaller f numbers mean wider apertures.) Try to compose the out-of-focus parts of the picture together with the main subject. Add one or two unedited sequences, together with relevant shooting data and an indication of your selects, to your learning log.”
I have been a little over the top here and used a 400mm lens and various apertures from wide open at F5.6 to show the shallow Depth of Field giving by longer lenses.
At f5.6, you can see the razor this depth of field and the increases in depth up to f16 after F16 the changes are not as visible.