The effect is actually pretty easy to achieve. To start off you’ll need a portrait photo, and preferably one with a single subject or couple standing close together, and with the subject close to the centre of the frame with plenty of room around the edges. Before you start you may want to use the crop tool to centre your subject. Ideally you want the frame to be centred on the subject’s upper body, so the head is toward the top of the frame, but still with plenty of room around the subject.
The actual vignette effect needs to be centred fairly accurately, so we’ll set up some guides to help us. In the View menu, click on Rulers (or use shortcut CTRL + ALT + R) to show the measuring bars around your image. Click on the ruler along the top of the image window and drag a guide line downwards to half way down your image. From the left-hand ruler, drag a guide rightwards to the centre of the image. Where the two lines cross is the centre point of your picture.
Click on the Selection Tool icon in the tool palette and hold for a second to bring up the tool sub-menu. Select the top one of the three tools, the marquee selection tool. In the tool options bar you’ll see a couple of options for this tool. In the Selection Type window, choose Ellipse.
Place your cursor over the centre cross of the guide lines, click and drag an elliptical shape out until it encompasses your portrait subject, but still leaves some clearance between the selection and the edge of the frame.