Lead-in lines are strong compositional elements that guide the viewer’s eye around the image, and draw the viewer’s focus towards the subject. For example, in a shot of a subject walking along a winding path, inclusion of the path in the foreground will create a lead-in line.
Equally, two rows of converging trees either side of your subject create converging lead-in lines that draw the viewer’s eye to their vanishing point behind the subject. By giving the eye a clear path to travel through the photograph, they help to make the image more visually appealing.
When the aperture is opened wide in order to blur the secondary elements of the image, lead-in lines can also add a powerful sense of depth, particularly where they are partially or fully blurred and the subject is sharp. This is because they clearly illustrate that the elements of the image are at different distances to each other, evidence by the shallow depth of focus.
Lead-in lines can be formed by natural or manmade elements and are not all that hard to find, if you look around you, think creatively and are prepared to change your angle. Even a wall can become a lead-in line when you shoot along it (not parallel to it), with the rows of bricks drawing the eye towards the subject. Repeated elements in a row can form an implied line, such as a sequence of equally spaced trees or rocks.
Even in full-frame portraits, the subject’s body can be positioned to create lead-in lines, by placing limbs where they will encourage the viewer’s eye to travel along them towards the subject’s face.
Diagonal lead-in lines, like diagonal background lines, add a sense of energy to compositions, so look for ways to add these to your portraits, starting them from one of the image corners for maximum compositional effect.