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Stock Photo / H South, licensed to About.com, Inc.
Expressions can drastically alter the shape of the eye. Pay attention to the planes, lines and wrinkles around the eye, not just the lids themselves, otherwise the eyes will just look mis-shapen. A smile pushes the muscles on the face upwards, making the lids bulge a little, sometimes making laugh-lines. Models practice an artificial smile that doesn't reach the eyes, but most subjects have smiles that affect their whole face.
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