Feathering is a technique I love to use when I want a soft, even light on my subject. This technique creates a much flatter light, no noticeable shadows.
When shooting at a 45 degree or 90 degree angle, the light coming from your softbox falls directly on your subject, and on the wall or backdrop behind the subject. Shooting this way is much like shooting a subject who is standing directly in front of a window. You will have bright highlights and dark shadows.
When you feather however, you move your softbox so that it is slightly in front or slightly above your subject, allowing the light to spill out from the edge of the softbox and fall on your subject. This is much like shooting a newborn or a toddler on the floor below a window or a person just to the right or left of a window.
Here is what a feathering set up looks like.
Feathering With Natural Light
Feathering With Strobe
In the photo below, the image on the left is shot with the softbox at 45 degrees to the subject. Notice the shadow on the right cheek and the color of the wall. In the image on the right, the softbox is 90 degrees, but it has been moved to be slightly in front of the bed, with the edge of the softbox about three inches in away from the doll. This allows the light to feather on my subject. Notice how even the light is now, and how much darker the wall appears.
In the photo below the image on the left is shot with the softbox positioned 90 degrees to my subject. The image on the right is feathered, creating even light on my subject and a darker backdrop.
Both of the examples above were shot with a digital camera so that you could really see the difference well! Film is much softer and less dramatic than digital. I have added a gallery of feathered images below so that you can see what the effect looks like on film.