Find a subject in front of a background with depth. Take a close viewpoint and zoom in; you’ll need to be aware of the minimum focusing distance of your lens. Focus on the subject and take a single shot. Then without changing the focal length, set the focus to infinity and take a second shot.
The closer you are to the subject, the shallower the depth of field, the further from the subject, the deeper the depth of field. That’s why macro shots taken from very close viewpoints have extremely shallow depth of field, and if you set the focus at infinity everything beyond a certain distance will be in focus.
As you review the two shots, how does the point of focus structure the composition? With a shallow depth of field the point of focus naturally draws the eye, which goes first of all to the part of the image that’s sharp. It generally feels more comfortable if the point of focus is in the foreground, although there’s nothing wrong with placing the point of focus in the background.
I had some difficulty finding something for this task. I went to Peel Castle hoping I would be able to find an opening to look through. Unfortunately it is now shut for the winter but I was able to walk up the stairs towards the entrance and tried these two shots through a window in the wall – it was hard to get the foreground shot as I was constrained for space between the two walls of the staircase.
You can see the bottom of the stones in the window frame clearly in this photo with the town appearing as a shallow depth of field in the background.
In the second image the stones of the window frame are blurred with the sharp background of the town and hill behind.
I then went for walk around the aside of the castle and did find further ‘windows’ in the wall as shown below. The scene through the window isn’t particularly scenic with just a view of rocks and sea but again one image shows the blurred window and sharp background with vice versa for the other image.