If you've mastered the backlighting and silhouette assignments this one should be technically quite easy. The difficult part will be in finding a suitable subject matter under the right lighting conditions.
Rim lighting is a special kind of backlighting that lights up the outer edges of the subject. With harder objects the backlighting bounces off the edges of the subject. With thin objects or fuzzy objects the light actually passes through the edges, causing them to be brighter than the center of the object.
To use rim lighting effectively the sun should be behind the subject but usually is not included in the frame. Behind the subject the background should be dark so that the rim lighting effect has something to contrast against.
Leaves and tree trunks, rounded or curvy objects and hair and fur are all great subjects for rim lighting. If you can enlist a friend to pose for you, position her in the direct sun with the dark shadows of a forest or building in the background. Watch how the sun lights up her hair.
Next time you watch a movie notice how frequently directors use backlighting and rim lighting to bathe their leading men and ladies in a golden aura.
Let's look at a few examples:
The intense winter sun is high and to the right and out of the frame in this photo of fluffy cattails. Light passes through the thick outer edge of fluff and is redirected towards the camera lens. The background is fairly bright also but contrasts enough to give a rim lighting effect.
Springtime is takenoko time in Japan. The gloom of a bamboo forest provides an ideal background while a thin shaft of light illuminates this bamboo sprout, highlighting the curves and rough texture at the edges.
The sun is hidden low and to the right of the clouds, its light only able to penetrate and pass through the very edges. Note the direction of the light, pointing up and away from the camera. As the light passes through the edges of the clouds some of it is redirected towards the camera, giving a dramatic rim lighting effect. The drama is enhanced by the dark center of the clouds through which light can barely pass.
All photographs were taken by Brian Grover.