A good standard for most lights is to place them one to one and-a-half times the diameter of the light from your subject. The Westcott Ring Light measures 18 inches in diameter (45 centimeters), so positioning the light 18 to 27 inches (45 to 68 centimeters) from the subject should create a nice quality of light with flattering falloff. This falloff will be more noticeable at close distances.
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